diff --git a/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/app/Mailer/config.yml b/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/app/Mailer/config.yml
index 7cb290dc24d5..c2c3ace06f17 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/app/Mailer/config.yml
+++ b/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/app/Mailer/config.yml
@@ -4,7 +4,7 @@ imports:
 
 framework:
     mailer:
-        dsn: 'smtp://null'
+        dsn: 'null://null'
         envelope:
             sender: sender@example.org
             recipients:
diff --git a/src/Symfony/Component/Mailer/Bridge/Amazon/Tests/Transport/SesApiTransportTest.php b/src/Symfony/Component/Mailer/Bridge/Amazon/Tests/Transport/SesApiTransportTest.php
new file mode 100644
index 000000000000..a1b0ae7f1a81
--- /dev/null
+++ b/src/Symfony/Component/Mailer/Bridge/Amazon/Tests/Transport/SesApiTransportTest.php
@@ -0,0 +1,48 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Mailer\Bridge\Amazon\Tests\Transport;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Mailer\Bridge\Amazon\Transport\SesApiTransport;
+
+class SesApiTransportTest extends TestCase
+{
+    /**
+     * @dataProvider getTransportData
+     */
+    public function testToString(SesApiTransport $transport, string $expected)
+    {
+        $this->assertSame($expected, (string) $transport);
+    }
+
+    public function getTransportData()
+    {
+        return [
+            [
+                new SesApiTransport('ACCESS_KEY', 'SECRET_KEY'),
+                'ses+api://ACCESS_KEY@email.eu-west-1.amazonaws.com',
+            ],
+            [
+                new SesApiTransport('ACCESS_KEY', 'SECRET_KEY', 'us-east-1'),
+                'ses+api://ACCESS_KEY@email.us-east-1.amazonaws.com',
+            ],
+            [
+                (new SesApiTransport('ACCESS_KEY', 'SECRET_KEY'))->setHost('example.com'),
+                'ses+api://ACCESS_KEY@example.com',
+            ],
+            [
+                (new SesApiTransport('ACCESS_KEY', 'SECRET_KEY'))->setHost('example.com')->setPort(99),
+                'ses+api://ACCESS_KEY@example.com:99',
+            ],
+        ];
+    }
+}
diff --git a/src/Symfony/Component/Mailer/Bridge/Amazon/Tests/Transport/SesHttpTransportTest.php b/src/Symfony/Component/Mailer/Bridge/Amazon/Tests/Transport/SesHttpTransportTest.php
new file mode 100644
index 000000000000..4e7cbd66aa15
--- /dev/null
+++ b/src/Symfony/Component/Mailer/Bridge/Amazon/Tests/Transport/SesHttpTransportTest.php
@@ -0,0 +1,48 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Mailer\Bridge\Amazon\Tests\Transport;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Mailer\Bridge\Amazon\Transport\SesHttpTransport;
+
+class SesHttpTransportTest extends TestCase
+{
+    /**
+     * @dataProvider getTransportData
+     */
+    public function testToString(SesHttpTransport $transport, string $expected)
+    {
+        $this->assertSame($expected, (string) $transport);
+    }
+
+    public function getTransportData()
+    {
+        return [
+            [
+                new SesHttpTransport('ACCESS_KEY', 'SECRET_KEY'),
+                'ses+https://ACCESS_KEY@email.eu-west-1.amazonaws.com',
+            ],
+            [
+                new SesHttpTransport('ACCESS_KEY', 'SECRET_KEY', 'us-east-1'),
+                'ses+https://ACCESS_KEY@email.us-east-1.amazonaws.com',
+            ],
+            [
+                (new SesHttpTransport('ACCESS_KEY', 'SECRET_KEY'))->setHost('example.com'),
+                'ses+https://ACCESS_KEY@example.com',
+            ],
+            [
+                (new SesHttpTransport('ACCESS_KEY', 'SECRET_KEY'))->setHost('example.com')->setPort(99),
+                'ses+https://ACCESS_KEY@example.com:99',
+            ],
+        ];
+    }
+}
diff --git a/src/Symfony/Component/Mailer/Bridge/Amazon/Tests/Transport/SesTransportFactoryTest.php b/src/Symfony/Component/Mailer/Bridge/Amazon/Tests/Transport/SesTransportFactoryTest.php
index 8e21f56f5044..7fada879ddc6 100644
--- a/src/Symfony/Component/Mailer/Bridge/Amazon/Tests/Transport/SesTransportFactoryTest.php
+++ b/src/Symfony/Component/Mailer/Bridge/Amazon/Tests/Transport/SesTransportFactoryTest.php
@@ -29,28 +29,33 @@ public function getFactory(): TransportFactoryInterface
     public function supportsProvider(): iterable
     {
         yield [
-            new Dsn('api', 'ses'),
+            new Dsn('ses+api', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('http', 'ses'),
+            new Dsn('ses+https', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtp', 'ses'),
+            new Dsn('ses', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtps', 'ses'),
+            new Dsn('ses+smtp', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtp', 'example.com'),
-            false,
+            new Dsn('ses+smtps', 'default'),
+            true,
+        ];
+
+        yield [
+            new Dsn('ses+smtp', 'example.com'),
+            true,
         ];
     }
 
@@ -61,37 +66,52 @@ public function createProvider(): iterable
         $logger = $this->getLogger();
 
         yield [
-            new Dsn('api', 'ses', self::USER, self::PASSWORD),
+            new Dsn('ses+api', 'default', self::USER, self::PASSWORD),
             new SesApiTransport(self::USER, self::PASSWORD, null, $client, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('api', 'ses', self::USER, self::PASSWORD, null, ['region' => 'eu-west-1']),
+            new Dsn('ses+api', 'default', self::USER, self::PASSWORD, null, ['region' => 'eu-west-1']),
             new SesApiTransport(self::USER, self::PASSWORD, 'eu-west-1', $client, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('http', 'ses', self::USER, self::PASSWORD),
+            new Dsn('ses+api', 'example.com', self::USER, self::PASSWORD, 8080),
+            (new SesApiTransport(self::USER, self::PASSWORD, null, $client, $dispatcher, $logger))->setHost('example.com')->setPort(8080),
+        ];
+
+        yield [
+            new Dsn('ses+https', 'default', self::USER, self::PASSWORD),
             new SesHttpTransport(self::USER, self::PASSWORD, null, $client, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('http', 'ses', self::USER, self::PASSWORD, null, ['region' => 'eu-west-1']),
+            new Dsn('ses', 'default', self::USER, self::PASSWORD),
+            new SesHttpTransport(self::USER, self::PASSWORD, null, $client, $dispatcher, $logger),
+        ];
+
+        yield [
+            new Dsn('ses+https', 'example.com', self::USER, self::PASSWORD, 8080),
+            (new SesHttpTransport(self::USER, self::PASSWORD, null, $client, $dispatcher, $logger))->setHost('example.com')->setPort(8080),
+        ];
+
+        yield [
+            new Dsn('ses+https', 'default', self::USER, self::PASSWORD, null, ['region' => 'eu-west-1']),
             new SesHttpTransport(self::USER, self::PASSWORD, 'eu-west-1', $client, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('smtp', 'ses', self::USER, self::PASSWORD),
+            new Dsn('ses+smtp', 'default', self::USER, self::PASSWORD),
             new SesSmtpTransport(self::USER, self::PASSWORD, null, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('smtp', 'ses', self::USER, self::PASSWORD, null, ['region' => 'eu-west-1']),
+            new Dsn('ses+smtp', 'default', self::USER, self::PASSWORD, null, ['region' => 'eu-west-1']),
             new SesSmtpTransport(self::USER, self::PASSWORD, 'eu-west-1', $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('smtps', 'ses', self::USER, self::PASSWORD, null, ['region' => 'eu-west-1']),
+            new Dsn('ses+smtps', 'default', self::USER, self::PASSWORD, null, ['region' => 'eu-west-1']),
             new SesSmtpTransport(self::USER, self::PASSWORD, 'eu-west-1', $dispatcher, $logger),
         ];
     }
@@ -99,15 +119,15 @@ public function createProvider(): iterable
     public function unsupportedSchemeProvider(): iterable
     {
         yield [
-            new Dsn('foo', 'ses', self::USER, self::PASSWORD),
-            'The "foo" scheme is not supported for mailer "ses". Supported schemes are: "api", "http", "smtp", "smtps".',
+            new Dsn('ses+foo', 'default', self::USER, self::PASSWORD),
+            'The "ses+foo" scheme is not supported. Supported schemes for mailer "ses" are: "ses", "ses+api", "ses+https", "ses+smtp", "ses+smtps".',
         ];
     }
 
     public function incompleteDsnProvider(): iterable
     {
-        yield [new Dsn('smtp', 'ses', self::USER)];
+        yield [new Dsn('ses+smtp', 'default', self::USER)];
 
-        yield [new Dsn('smtp', 'ses', null, self::PASSWORD)];
+        yield [new Dsn('ses+smtp', 'default', null, self::PASSWORD)];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesApiTransport.php b/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesApiTransport.php
index 6bd2b2cb9a00..1bfa9db341d2 100644
--- a/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesApiTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesApiTransport.php
@@ -25,7 +25,7 @@
  */
 class SesApiTransport extends AbstractApiTransport
 {
-    private const ENDPOINT = 'https://email.%region%.amazonaws.com';
+    private const HOST = 'email.%region%.amazonaws.com';
 
     private $accessKey;
     private $secretKey;
@@ -45,7 +45,7 @@ public function __construct(string $accessKey, string $secretKey, string $region
 
     public function __toString(): string
     {
-        return sprintf('api://%s@ses?region=%s', $this->accessKey, $this->region);
+        return sprintf('ses+api://%s@%s', $this->accessKey, $this->getEndpoint());
     }
 
     protected function doSendApi(Email $email, SmtpEnvelope $envelope): ResponseInterface
@@ -53,8 +53,7 @@ protected function doSendApi(Email $email, SmtpEnvelope $envelope): ResponseInte
         $date = gmdate('D, d M Y H:i:s e');
         $auth = sprintf('AWS3-HTTPS AWSAccessKeyId=%s,Algorithm=HmacSHA256,Signature=%s', $this->accessKey, $this->getSignature($date));
 
-        $endpoint = str_replace('%region%', $this->region, self::ENDPOINT);
-        $response = $this->client->request('POST', $endpoint, [
+        $response = $this->client->request('POST', 'https://'.$this->getEndpoint(), [
             'headers' => [
                 'X-Amzn-Authorization' => $auth,
                 'Date' => $date,
@@ -72,6 +71,11 @@ protected function doSendApi(Email $email, SmtpEnvelope $envelope): ResponseInte
         return $response;
     }
 
+    private function getEndpoint(): ?string
+    {
+        return ($this->host ?: str_replace('%region%', $this->region, self::HOST)).($this->port ? ':'.$this->port : '');
+    }
+
     private function getSignature(string $string): string
     {
         return base64_encode(hash_hmac('sha256', $string, $this->secretKey, true));
diff --git a/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesHttpTransport.php b/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesHttpTransport.php
index 202aef7baa1f..be828b0dfc9e 100644
--- a/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesHttpTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesHttpTransport.php
@@ -24,7 +24,7 @@
  */
 class SesHttpTransport extends AbstractHttpTransport
 {
-    private const ENDPOINT = 'https://email.%region%.amazonaws.com';
+    private const HOST = 'email.%region%.amazonaws.com';
 
     private $accessKey;
     private $secretKey;
@@ -44,7 +44,7 @@ public function __construct(string $accessKey, string $secretKey, string $region
 
     public function __toString(): string
     {
-        return sprintf('http://%s@ses?region=%s', $this->accessKey, $this->region);
+        return sprintf('ses+https://%s@%s', $this->accessKey, $this->getEndpoint());
     }
 
     protected function doSendHttp(SentMessage $message): ResponseInterface
@@ -52,8 +52,7 @@ protected function doSendHttp(SentMessage $message): ResponseInterface
         $date = gmdate('D, d M Y H:i:s e');
         $auth = sprintf('AWS3-HTTPS AWSAccessKeyId=%s,Algorithm=HmacSHA256,Signature=%s', $this->accessKey, $this->getSignature($date));
 
-        $endpoint = str_replace('%region%', $this->region, self::ENDPOINT);
-        $response = $this->client->request('POST', $endpoint, [
+        $response = $this->client->request('POST', 'https://'.$this->getEndpoint(), [
             'headers' => [
                 'X-Amzn-Authorization' => $auth,
                 'Date' => $date,
@@ -73,6 +72,11 @@ protected function doSendHttp(SentMessage $message): ResponseInterface
         return $response;
     }
 
+    private function getEndpoint(): ?string
+    {
+        return ($this->host ?: str_replace('%region%', $this->region, self::HOST)).($this->port ? ':'.$this->port : '');
+    }
+
     private function getSignature(string $string): string
     {
         return base64_encode(hash_hmac('sha256', $string, $this->secretKey, true));
diff --git a/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesTransportFactory.php b/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesTransportFactory.php
index 0dba1d998b46..5977d2f37682 100644
--- a/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesTransportFactory.php
+++ b/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesTransportFactory.php
@@ -27,24 +27,26 @@ public function create(Dsn $dsn): TransportInterface
         $user = $this->getUser($dsn);
         $password = $this->getPassword($dsn);
         $region = $dsn->getOption('region');
+        $host = 'default' === $dsn->getHost() ? null : $dsn->getHost();
+        $port = $dsn->getPort();
 
-        if ('api' === $scheme) {
-            return new SesApiTransport($user, $password, $region, $this->client, $this->dispatcher, $this->logger);
+        if ('ses+api' === $scheme) {
+            return (new SesApiTransport($user, $password, $region, $this->client, $this->dispatcher, $this->logger))->setHost($host)->setPort($port);
         }
 
-        if ('http' === $scheme) {
-            return new SesHttpTransport($user, $password, $region, $this->client, $this->dispatcher, $this->logger);
+        if ('ses+https' === $scheme || 'ses' === $scheme) {
+            return (new SesHttpTransport($user, $password, $region, $this->client, $this->dispatcher, $this->logger))->setHost($host)->setPort($port);
         }
 
-        if ('smtp' === $scheme || 'smtps' === $scheme) {
+        if ('ses+smtp' === $scheme || 'ses+smtps' === $scheme) {
             return new SesSmtpTransport($user, $password, $region, $this->dispatcher, $this->logger);
         }
 
-        throw new UnsupportedSchemeException($dsn, ['api', 'http', 'smtp', 'smtps']);
+        throw new UnsupportedSchemeException($dsn, 'ses', $this->getSupportedSchemes());
     }
 
-    public function supports(Dsn $dsn): bool
+    protected function getSupportedSchemes(): array
     {
-        return 'ses' === $dsn->getHost();
+        return ['ses', 'ses+api', 'ses+https', 'ses+smtp', 'ses+smtps'];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Google/Tests/Transport/GmailTransportFactoryTest.php b/src/Symfony/Component/Mailer/Bridge/Google/Tests/Transport/GmailTransportFactoryTest.php
index 803b3b4e2473..456be7848306 100644
--- a/src/Symfony/Component/Mailer/Bridge/Google/Tests/Transport/GmailTransportFactoryTest.php
+++ b/src/Symfony/Component/Mailer/Bridge/Google/Tests/Transport/GmailTransportFactoryTest.php
@@ -18,30 +18,40 @@ public function getFactory(): TransportFactoryInterface
     public function supportsProvider(): iterable
     {
         yield [
-            new Dsn('smtp', 'gmail'),
+            new Dsn('gmail', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtps', 'gmail'),
+            new Dsn('gmail+smtp', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtp', 'example.com'),
-            false,
+            new Dsn('gmail+smtps', 'default'),
+            true,
+        ];
+
+        yield [
+            new Dsn('gmail+smtp', 'example.com'),
+            true,
         ];
     }
 
     public function createProvider(): iterable
     {
         yield [
-            new Dsn('smtp', 'gmail', self::USER, self::PASSWORD),
+            new Dsn('gmail', 'default', self::USER, self::PASSWORD),
+            new GmailSmtpTransport(self::USER, self::PASSWORD, $this->getDispatcher(), $this->getLogger()),
+        ];
+
+        yield [
+            new Dsn('gmail+smtp', 'default', self::USER, self::PASSWORD),
             new GmailSmtpTransport(self::USER, self::PASSWORD, $this->getDispatcher(), $this->getLogger()),
         ];
 
         yield [
-            new Dsn('smtps', 'gmail', self::USER, self::PASSWORD),
+            new Dsn('gmail+smtps', 'default', self::USER, self::PASSWORD),
             new GmailSmtpTransport(self::USER, self::PASSWORD, $this->getDispatcher(), $this->getLogger()),
         ];
     }
@@ -49,15 +59,15 @@ public function createProvider(): iterable
     public function unsupportedSchemeProvider(): iterable
     {
         yield [
-            new Dsn('foo', 'gmail', self::USER, self::PASSWORD),
-            'The "foo" scheme is not supported for mailer "gmail". Supported schemes are: "smtp", "smtps".',
+            new Dsn('gmail+foo', 'default', self::USER, self::PASSWORD),
+            'The "gmail+foo" scheme is not supported. Supported schemes for mailer "gmail" are: "gmail", "gmail+smtp", "gmail+smtps".',
         ];
     }
 
     public function incompleteDsnProvider(): iterable
     {
-        yield [new Dsn('smtp', 'gmail', self::USER)];
+        yield [new Dsn('gmail+smtp', 'default', self::USER)];
 
-        yield [new Dsn('smtp', 'gmail', null, self::PASSWORD)];
+        yield [new Dsn('gmail+smtp', 'default', null, self::PASSWORD)];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Google/Transport/GmailTransportFactory.php b/src/Symfony/Component/Mailer/Bridge/Google/Transport/GmailTransportFactory.php
index 346a2a7e93a4..8a0bd5626699 100644
--- a/src/Symfony/Component/Mailer/Bridge/Google/Transport/GmailTransportFactory.php
+++ b/src/Symfony/Component/Mailer/Bridge/Google/Transport/GmailTransportFactory.php
@@ -23,15 +23,15 @@ final class GmailTransportFactory extends AbstractTransportFactory
 {
     public function create(Dsn $dsn): TransportInterface
     {
-        if ('smtp' === $dsn->getScheme() || 'smtps' === $dsn->getScheme()) {
+        if (\in_array($dsn->getScheme(), $this->getSupportedSchemes())) {
             return new GmailSmtpTransport($this->getUser($dsn), $this->getPassword($dsn), $this->dispatcher, $this->logger);
         }
 
-        throw new UnsupportedSchemeException($dsn, ['smtp', 'smtps']);
+        throw new UnsupportedSchemeException($dsn, 'gmail', $this->getSupportedSchemes());
     }
 
-    public function supports(Dsn $dsn): bool
+    protected function getSupportedSchemes(): array
     {
-        return 'gmail' === $dsn->getHost();
+        return ['gmail', 'gmail+smtp', 'gmail+smtps'];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Tests/Transport/MandrillApiTransportTest.php b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Tests/Transport/MandrillApiTransportTest.php
new file mode 100644
index 000000000000..2bec48281842
--- /dev/null
+++ b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Tests/Transport/MandrillApiTransportTest.php
@@ -0,0 +1,44 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Mailer\Bridge\Mailchimp\Tests\Transport;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Mailer\Bridge\Mailchimp\Transport\MandrillApiTransport;
+
+class MandrillApiTransportTest extends TestCase
+{
+    /**
+     * @dataProvider getTransportData
+     */
+    public function testToString(MandrillApiTransport $transport, string $expected)
+    {
+        $this->assertSame($expected, (string) $transport);
+    }
+
+    public function getTransportData()
+    {
+        return [
+            [
+                new MandrillApiTransport('KEY'),
+                'mandrill+api://mandrillapp.com',
+            ],
+            [
+                (new MandrillApiTransport('KEY'))->setHost('example.com'),
+                'mandrill+api://example.com',
+            ],
+            [
+                (new MandrillApiTransport('KEY'))->setHost('example.com')->setPort(99),
+                'mandrill+api://example.com:99',
+            ],
+        ];
+    }
+}
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Tests/Transport/MandrillHttpTransportTest.php b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Tests/Transport/MandrillHttpTransportTest.php
new file mode 100644
index 000000000000..dd72c848f14f
--- /dev/null
+++ b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Tests/Transport/MandrillHttpTransportTest.php
@@ -0,0 +1,44 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Mailer\Bridge\Mailchimp\Tests\Transport;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Mailer\Bridge\Mailchimp\Transport\MandrillHttpTransport;
+
+class MandrillHttpTransportTest extends TestCase
+{
+    /**
+     * @dataProvider getTransportData
+     */
+    public function testToString(MandrillHttpTransport $transport, string $expected)
+    {
+        $this->assertSame($expected, (string) $transport);
+    }
+
+    public function getTransportData()
+    {
+        return [
+            [
+                new MandrillHttpTransport('KEY'),
+                'mandrill+https://mandrillapp.com',
+            ],
+            [
+                (new MandrillHttpTransport('KEY'))->setHost('example.com'),
+                'mandrill+https://example.com',
+            ],
+            [
+                (new MandrillHttpTransport('KEY'))->setHost('example.com')->setPort(99),
+                'mandrill+https://example.com:99',
+            ],
+        ];
+    }
+}
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Tests/Transport/MandrillTransportFactoryTest.php b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Tests/Transport/MandrillTransportFactoryTest.php
index 2e8e2c0c0cc7..317cbb35cdcf 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Tests/Transport/MandrillTransportFactoryTest.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Tests/Transport/MandrillTransportFactoryTest.php
@@ -29,28 +29,33 @@ public function getFactory(): TransportFactoryInterface
     public function supportsProvider(): iterable
     {
         yield [
-            new Dsn('api', 'mandrill'),
+            new Dsn('mandrill', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('http', 'mandrill'),
+            new Dsn('mandrill+api', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtp', 'mandrill'),
+            new Dsn('mandrill+https', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtps', 'mandrill'),
+            new Dsn('mandrill+smtp', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtp', 'example.com'),
-            false,
+            new Dsn('mandrill+smtps', 'default'),
+            true,
+        ];
+
+        yield [
+            new Dsn('mandrill+smtp', 'example.com'),
+            true,
         ];
     }
 
@@ -61,22 +66,37 @@ public function createProvider(): iterable
         $logger = $this->getLogger();
 
         yield [
-            new Dsn('api', 'mandrill', self::USER),
+            new Dsn('mandrill+api', 'default', self::USER),
             new MandrillApiTransport(self::USER, $client, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('http', 'mandrill', self::USER),
+            new Dsn('mandrill+api', 'example.com', self::USER, '', 8080),
+            (new MandrillApiTransport(self::USER, $client, $dispatcher, $logger))->setHost('example.com')->setPort(8080),
+        ];
+
+        yield [
+            new Dsn('mandrill', 'default', self::USER),
             new MandrillHttpTransport(self::USER, $client, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('smtp', 'mandrill', self::USER, self::PASSWORD),
+            new Dsn('mandrill+https', 'default', self::USER),
+            new MandrillHttpTransport(self::USER, $client, $dispatcher, $logger),
+        ];
+
+        yield [
+            new Dsn('mandrill+https', 'example.com', self::USER, '', 8080),
+            (new MandrillHttpTransport(self::USER, $client, $dispatcher, $logger))->setHost('example.com')->setPort(8080),
+        ];
+
+        yield [
+            new Dsn('mandrill+smtp', 'default', self::USER, self::PASSWORD),
             new MandrillSmtpTransport(self::USER, self::PASSWORD, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('smtps', 'mandrill', self::USER, self::PASSWORD),
+            new Dsn('mandrill+smtps', 'default', self::USER, self::PASSWORD),
             new MandrillSmtpTransport(self::USER, self::PASSWORD, $dispatcher, $logger),
         ];
     }
@@ -84,15 +104,15 @@ public function createProvider(): iterable
     public function unsupportedSchemeProvider(): iterable
     {
         yield [
-            new Dsn('foo', 'mandrill', self::USER),
-            'The "foo" scheme is not supported for mailer "mandrill". Supported schemes are: "api", "http", "smtp", "smtps".',
+            new Dsn('mandrill+foo', 'default', self::USER),
+            'The "mandrill+foo" scheme is not supported. Supported schemes for mailer "mandrill" are: "mandrill", "mandrill+api", "mandrill+https", "mandrill+smtp", "mandrill+smtps".',
         ];
     }
 
     public function incompleteDsnProvider(): iterable
     {
-        yield [new Dsn('api', 'mandrill')];
+        yield [new Dsn('mandrill+api', 'default')];
 
-        yield [new Dsn('smtp', 'mandrill', self::USER)];
+        yield [new Dsn('mandrill+smtp', 'default', self::USER)];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillApiTransport.php b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillApiTransport.php
index 879611b88484..904f66994c58 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillApiTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillApiTransport.php
@@ -25,7 +25,7 @@
  */
 class MandrillApiTransport extends AbstractApiTransport
 {
-    private const ENDPOINT = 'https://mandrillapp.com/api/1.0/messages/send.json';
+    private const HOST = 'mandrillapp.com';
 
     private $key;
 
@@ -38,12 +38,12 @@ public function __construct(string $key, HttpClientInterface $client = null, Eve
 
     public function __toString(): string
     {
-        return sprintf('api://mandrill');
+        return sprintf('mandrill+api://%s', $this->getEndpoint());
     }
 
     protected function doSendApi(Email $email, SmtpEnvelope $envelope): ResponseInterface
     {
-        $response = $this->client->request('POST', self::ENDPOINT, [
+        $response = $this->client->request('POST', 'https://'.$this->getEndpoint().'/api/1.0/messages/send.json', [
             'json' => $this->getPayload($email, $envelope),
         ]);
 
@@ -59,6 +59,11 @@ protected function doSendApi(Email $email, SmtpEnvelope $envelope): ResponseInte
         return $response;
     }
 
+    private function getEndpoint(): ?string
+    {
+        return ($this->host ?: self::HOST).($this->port ? ':'.$this->port : '');
+    }
+
     private function getPayload(Email $email, SmtpEnvelope $envelope): array
     {
         $payload = [
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillHttpTransport.php b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillHttpTransport.php
index a24afa86a8e9..cec26aaf03d0 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillHttpTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillHttpTransport.php
@@ -24,7 +24,7 @@
  */
 class MandrillHttpTransport extends AbstractHttpTransport
 {
-    private const ENDPOINT = 'https://mandrillapp.com/api/1.0/messages/send-raw.json';
+    private const HOST = 'mandrillapp.com';
     private $key;
 
     public function __construct(string $key, HttpClientInterface $client = null, EventDispatcherInterface $dispatcher = null, LoggerInterface $logger = null)
@@ -36,13 +36,13 @@ public function __construct(string $key, HttpClientInterface $client = null, Eve
 
     public function __toString(): string
     {
-        return sprintf('http://mandrill');
+        return sprintf('mandrill+https://%s', $this->getEndpoint());
     }
 
     protected function doSendHttp(SentMessage $message): ResponseInterface
     {
         $envelope = $message->getEnvelope();
-        $response = $this->client->request('POST', self::ENDPOINT, [
+        $response = $this->client->request('POST', 'https://'.$this->getEndpoint().'/api/1.0/messages/send-raw.json', [
             'json' => [
                 'key' => $this->key,
                 'to' => $this->stringifyAddresses($envelope->getRecipients()),
@@ -62,4 +62,9 @@ protected function doSendHttp(SentMessage $message): ResponseInterface
 
         return $response;
     }
+
+    private function getEndpoint(): ?string
+    {
+        return ($this->host ?: self::HOST).($this->port ? ':'.$this->port : '');
+    }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillTransportFactory.php b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillTransportFactory.php
index b00b2bee748e..1ba963e00d7d 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillTransportFactory.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillTransportFactory.php
@@ -25,26 +25,28 @@ public function create(Dsn $dsn): TransportInterface
     {
         $scheme = $dsn->getScheme();
         $user = $this->getUser($dsn);
+        $host = 'default' === $dsn->getHost() ? null : $dsn->getHost();
+        $port = $dsn->getPort();
 
-        if ('api' === $scheme) {
-            return new MandrillApiTransport($user, $this->client, $this->dispatcher, $this->logger);
+        if ('mandrill+api' === $scheme) {
+            return (new MandrillApiTransport($user, $this->client, $this->dispatcher, $this->logger))->setHost($host)->setPort($port);
         }
 
-        if ('http' === $scheme) {
-            return new MandrillHttpTransport($user, $this->client, $this->dispatcher, $this->logger);
+        if ('mandrill+https' === $scheme || 'mandrill' === $scheme) {
+            return (new MandrillHttpTransport($user, $this->client, $this->dispatcher, $this->logger))->setHost($host)->setPort($port);
         }
 
-        if ('smtp' === $scheme || 'smtps' === $scheme) {
+        if ('mandrill+smtp' === $scheme || 'mandrill+smtps' === $scheme) {
             $password = $this->getPassword($dsn);
 
             return new MandrillSmtpTransport($user, $password, $this->dispatcher, $this->logger);
         }
 
-        throw new UnsupportedSchemeException($dsn, ['api', 'http', 'smtp', 'smtps']);
+        throw new UnsupportedSchemeException($dsn, 'mandrill', $this->getSupportedSchemes());
     }
 
-    public function supports(Dsn $dsn): bool
+    protected function getSupportedSchemes(): array
     {
-        return 'mandrill' === $dsn->getHost();
+        return ['mandrill', 'mandrill+api', 'mandrill+https', 'mandrill+smtp', 'mandrill+smtps'];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailgun/Tests/Transport/MailgunApiTransportTest.php b/src/Symfony/Component/Mailer/Bridge/Mailgun/Tests/Transport/MailgunApiTransportTest.php
new file mode 100644
index 000000000000..eb9838390aed
--- /dev/null
+++ b/src/Symfony/Component/Mailer/Bridge/Mailgun/Tests/Transport/MailgunApiTransportTest.php
@@ -0,0 +1,48 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Mailer\Bridge\Mailgun\Tests\Transport;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Mailer\Bridge\Mailgun\Transport\MailgunApiTransport;
+
+class MailgunApiTransportTest extends TestCase
+{
+    /**
+     * @dataProvider getTransportData
+     */
+    public function testToString(MailgunApiTransport $transport, string $expected)
+    {
+        $this->assertSame($expected, (string) $transport);
+    }
+
+    public function getTransportData()
+    {
+        return [
+            [
+                new MailgunApiTransport('ACCESS_KEY', 'DOMAIN'),
+                'mailgun+api://api.mailgun.net?domain=DOMAIN',
+            ],
+            [
+                new MailgunApiTransport('ACCESS_KEY', 'DOMAIN', 'us-east-1'),
+                'mailgun+api://api.us-east-1.mailgun.net?domain=DOMAIN',
+            ],
+            [
+                (new MailgunApiTransport('ACCESS_KEY', 'DOMAIN'))->setHost('example.com'),
+                'mailgun+api://example.com?domain=DOMAIN',
+            ],
+            [
+                (new MailgunApiTransport('ACCESS_KEY', 'DOMAIN'))->setHost('example.com')->setPort(99),
+                'mailgun+api://example.com:99?domain=DOMAIN',
+            ],
+        ];
+    }
+}
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailgun/Tests/Transport/MailgunHttpTransportTest.php b/src/Symfony/Component/Mailer/Bridge/Mailgun/Tests/Transport/MailgunHttpTransportTest.php
new file mode 100644
index 000000000000..9b57b2b35e77
--- /dev/null
+++ b/src/Symfony/Component/Mailer/Bridge/Mailgun/Tests/Transport/MailgunHttpTransportTest.php
@@ -0,0 +1,48 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Mailer\Bridge\Mailgun\Tests\Transport;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Mailer\Bridge\Mailgun\Transport\MailgunHttpTransport;
+
+class MailgunHttpTransportTest extends TestCase
+{
+    /**
+     * @dataProvider getTransportData
+     */
+    public function testToString(MailgunHttpTransport $transport, string $expected)
+    {
+        $this->assertSame($expected, (string) $transport);
+    }
+
+    public function getTransportData()
+    {
+        return [
+            [
+                new MailgunHttpTransport('ACCESS_KEY', 'DOMAIN'),
+                'mailgun+https://api.mailgun.net?domain=DOMAIN',
+            ],
+            [
+                new MailgunHttpTransport('ACCESS_KEY', 'DOMAIN', 'us-east-1'),
+                'mailgun+https://api.us-east-1.mailgun.net?domain=DOMAIN',
+            ],
+            [
+                (new MailgunHttpTransport('ACCESS_KEY', 'DOMAIN'))->setHost('example.com'),
+                'mailgun+https://example.com?domain=DOMAIN',
+            ],
+            [
+                (new MailgunHttpTransport('ACCESS_KEY', 'DOMAIN'))->setHost('example.com')->setPort(99),
+                'mailgun+https://example.com:99?domain=DOMAIN',
+            ],
+        ];
+    }
+}
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailgun/Tests/Transport/MailgunTransportFactoryTest.php b/src/Symfony/Component/Mailer/Bridge/Mailgun/Tests/Transport/MailgunTransportFactoryTest.php
index 829d880fca62..67a3ed51c429 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailgun/Tests/Transport/MailgunTransportFactoryTest.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailgun/Tests/Transport/MailgunTransportFactoryTest.php
@@ -29,28 +29,33 @@ public function getFactory(): TransportFactoryInterface
     public function supportsProvider(): iterable
     {
         yield [
-            new Dsn('api', 'mailgun'),
+            new Dsn('mailgun+api', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('http', 'mailgun'),
+            new Dsn('mailgun', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtp', 'mailgun'),
+            new Dsn('mailgun+https', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtps', 'mailgun'),
+            new Dsn('mailgun+smtp', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtp', 'example.com'),
-            false,
+            new Dsn('mailgun+smtps', 'default'),
+            true,
+        ];
+
+        yield [
+            new Dsn('mailgun+smtp', 'example.com'),
+            true,
         ];
     }
 
@@ -61,27 +66,42 @@ public function createProvider(): iterable
         $logger = $this->getLogger();
 
         yield [
-            new Dsn('api', 'mailgun', self::USER, self::PASSWORD),
+            new Dsn('mailgun+api', 'default', self::USER, self::PASSWORD),
             new MailgunApiTransport(self::USER, self::PASSWORD, null, $client, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('api', 'mailgun', self::USER, self::PASSWORD, null, ['region' => 'eu']),
+            new Dsn('mailgun+api', 'default', self::USER, self::PASSWORD, null, ['region' => 'eu']),
             new MailgunApiTransport(self::USER, self::PASSWORD, 'eu', $client, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('http', 'mailgun', self::USER, self::PASSWORD),
+            new Dsn('mailgun+api', 'example.com', self::USER, self::PASSWORD, 8080),
+            (new MailgunApiTransport(self::USER, self::PASSWORD, null, $client, $dispatcher, $logger))->setHost('example.com')->setPort(8080),
+        ];
+
+        yield [
+            new Dsn('mailgun', 'default', self::USER, self::PASSWORD),
             new MailgunHttpTransport(self::USER, self::PASSWORD, null, $client, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('smtp', 'mailgun', self::USER, self::PASSWORD),
+            new Dsn('mailgun+https', 'default', self::USER, self::PASSWORD),
+            new MailgunHttpTransport(self::USER, self::PASSWORD, null, $client, $dispatcher, $logger),
+        ];
+
+        yield [
+            new Dsn('mailgun+https', 'example.com', self::USER, self::PASSWORD, 8080),
+            (new MailgunHttpTransport(self::USER, self::PASSWORD, null, $client, $dispatcher, $logger))->setHost('example.com')->setPort(8080),
+        ];
+
+        yield [
+            new Dsn('mailgun+smtp', 'default', self::USER, self::PASSWORD),
             new MailgunSmtpTransport(self::USER, self::PASSWORD, null, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('smtps', 'mailgun', self::USER, self::PASSWORD),
+            new Dsn('mailgun+smtps', 'default', self::USER, self::PASSWORD),
             new MailgunSmtpTransport(self::USER, self::PASSWORD, null, $dispatcher, $logger),
         ];
     }
@@ -89,15 +109,15 @@ public function createProvider(): iterable
     public function unsupportedSchemeProvider(): iterable
     {
         yield [
-            new Dsn('foo', 'mailgun', self::USER, self::PASSWORD),
-            'The "foo" scheme is not supported for mailer "mailgun". Supported schemes are: "api", "http", "smtp", "smtps".',
+            new Dsn('mailgun+foo', 'default', self::USER, self::PASSWORD),
+            'The "mailgun+foo" scheme is not supported. Supported schemes for mailer "mailgun" are: "mailgun", "mailgun+api", "mailgun+https", "mailgun+smtp", "mailgun+smtps".',
         ];
     }
 
     public function incompleteDsnProvider(): iterable
     {
-        yield [new Dsn('api', 'mailgun', self::USER)];
+        yield [new Dsn('mailgun+api', 'default', self::USER)];
 
-        yield [new Dsn('api', 'mailgun', null, self::PASSWORD)];
+        yield [new Dsn('mailgun+api', 'default', null, self::PASSWORD)];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunApiTransport.php b/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunApiTransport.php
index f58e18373688..1838a0106150 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunApiTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunApiTransport.php
@@ -26,7 +26,7 @@
  */
 class MailgunApiTransport extends AbstractApiTransport
 {
-    private const ENDPOINT = 'https://api.%region_dot%mailgun.net/v3/%domain%/messages';
+    private const HOST = 'api.%region_dot%mailgun.net';
 
     private $key;
     private $domain;
@@ -43,7 +43,7 @@ public function __construct(string $key, string $domain, string $region = null,
 
     public function __toString(): string
     {
-        return sprintf('api://%s@mailgun?region=%s', $this->domain, $this->region);
+        return sprintf('mailgun+api://%s?domain=%s', $this->getEndpoint(), $this->domain);
     }
 
     protected function doSendApi(Email $email, SmtpEnvelope $envelope): ResponseInterface
@@ -54,8 +54,8 @@ protected function doSendApi(Email $email, SmtpEnvelope $envelope): ResponseInte
             $headers[] = $header->toString();
         }
 
-        $endpoint = str_replace(['%domain%', '%region_dot%'], [urlencode($this->domain), 'us' !== ($this->region ?: 'us') ? $this->region.'.' : ''], self::ENDPOINT);
-        $response = $this->client->request('POST', $endpoint, [
+        $endpoint = str_replace('%domain%', urlencode($this->domain), $this->getEndpoint()).'/v3/%domain%/messages';
+        $response = $this->client->request('POST', 'https://'.$endpoint, [
             'auth_basic' => 'api:'.$this->key,
             'headers' => $headers,
             'body' => $body->bodyToIterable(),
@@ -137,4 +137,11 @@ private function prepareAttachments(Email $email, ?string $html): array
 
         return [$attachments, $inlines, $html];
     }
+
+    private function getEndpoint(): ?string
+    {
+        $host = $this->host ?: str_replace('%region_dot%', 'us' !== ($this->region ?: 'us') ? $this->region.'.' : '', self::HOST);
+
+        return $host.($this->port ? ':'.$this->port : '');
+    }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunHttpTransport.php b/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunHttpTransport.php
index ad77efea6be7..b5c9db3ba72b 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunHttpTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunHttpTransport.php
@@ -26,7 +26,8 @@
  */
 class MailgunHttpTransport extends AbstractHttpTransport
 {
-    private const ENDPOINT = 'https://api.%region_dot%mailgun.net/v3/%domain%/messages.mime';
+    private const HOST = 'api.%region_dot%mailgun.net';
+
     private $key;
     private $domain;
     private $region;
@@ -42,7 +43,7 @@ public function __construct(string $key, string $domain, string $region = null,
 
     public function __toString(): string
     {
-        return sprintf('http://%s@mailgun?region=%s', $this->domain, $this->region);
+        return sprintf('mailgun+https://%s?domain=%s', $this->getEndpoint(), $this->domain);
     }
 
     protected function doSendHttp(SentMessage $message): ResponseInterface
@@ -55,8 +56,9 @@ protected function doSendHttp(SentMessage $message): ResponseInterface
         foreach ($body->getPreparedHeaders()->all() as $header) {
             $headers[] = $header->toString();
         }
-        $endpoint = str_replace(['%domain%', '%region_dot%'], [urlencode($this->domain), 'us' !== ($this->region ?: 'us') ? $this->region.'.' : ''], self::ENDPOINT);
-        $response = $this->client->request('POST', $endpoint, [
+
+        $endpoint = str_replace('%domain%', urlencode($this->domain), $this->getEndpoint()).'/v3/%domain%/messages.mime';
+        $response = $this->client->request('POST', 'https://'.$endpoint, [
             'auth_basic' => 'api:'.$this->key,
             'headers' => $headers,
             'body' => $body->bodyToIterable(),
@@ -70,4 +72,11 @@ protected function doSendHttp(SentMessage $message): ResponseInterface
 
         return $response;
     }
+
+    private function getEndpoint(): ?string
+    {
+        $host = $this->host ?: str_replace('%region_dot%', 'us' !== ($this->region ?: 'us') ? $this->region.'.' : '', self::HOST);
+
+        return $host.($this->port ? ':'.$this->port : '');
+    }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunTransportFactory.php b/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunTransportFactory.php
index 486dd6661935..c238f832fae8 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunTransportFactory.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunTransportFactory.php
@@ -27,24 +27,26 @@ public function create(Dsn $dsn): TransportInterface
         $user = $this->getUser($dsn);
         $password = $this->getPassword($dsn);
         $region = $dsn->getOption('region');
+        $host = 'default' === $dsn->getHost() ? null : $dsn->getHost();
+        $port = $dsn->getPort();
 
-        if ('api' === $scheme) {
-            return new MailgunApiTransport($user, $password, $region, $this->client, $this->dispatcher, $this->logger);
+        if ('mailgun+api' === $scheme) {
+            return (new MailgunApiTransport($user, $password, $region, $this->client, $this->dispatcher, $this->logger))->setHost($host)->setPort($port);
         }
 
-        if ('http' === $scheme) {
-            return new MailgunHttpTransport($user, $password, $region, $this->client, $this->dispatcher, $this->logger);
+        if ('mailgun+https' === $scheme || 'mailgun' === $scheme) {
+            return (new MailgunHttpTransport($user, $password, $region, $this->client, $this->dispatcher, $this->logger))->setHost($host)->setPort($port);
         }
 
-        if ('smtp' === $scheme || 'smtps' === $scheme) {
+        if ('mailgun+smtp' === $scheme || 'mailgun+smtps' === $scheme) {
             return new MailgunSmtpTransport($user, $password, $region, $this->dispatcher, $this->logger);
         }
 
-        throw new UnsupportedSchemeException($dsn, ['api', 'http', 'smtp', 'smtps']);
+        throw new UnsupportedSchemeException($dsn, 'mailgun', $this->getSupportedSchemes());
     }
 
-    public function supports(Dsn $dsn): bool
+    protected function getSupportedSchemes(): array
     {
-        return 'mailgun' === $dsn->getHost();
+        return ['mailgun', 'mailgun+api', 'mailgun+https', 'mailgun+smtp', 'mailgun+smtps'];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Postmark/Tests/Transport/PostmarkApiTransportTest.php b/src/Symfony/Component/Mailer/Bridge/Postmark/Tests/Transport/PostmarkApiTransportTest.php
new file mode 100644
index 000000000000..b6568706f830
--- /dev/null
+++ b/src/Symfony/Component/Mailer/Bridge/Postmark/Tests/Transport/PostmarkApiTransportTest.php
@@ -0,0 +1,44 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Mailer\Bridge\Postmark\Tests\Transport;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Mailer\Bridge\Postmark\Transport\PostmarkApiTransport;
+
+class PostmarkApiTransportTest extends TestCase
+{
+    /**
+     * @dataProvider getTransportData
+     */
+    public function testToString(PostmarkApiTransport $transport, string $expected)
+    {
+        $this->assertSame($expected, (string) $transport);
+    }
+
+    public function getTransportData()
+    {
+        return [
+            [
+                new PostmarkApiTransport('KEY'),
+                'postmark+api://api.postmarkapp.com',
+            ],
+            [
+                (new PostmarkApiTransport('KEY'))->setHost('example.com'),
+                'postmark+api://example.com',
+            ],
+            [
+                (new PostmarkApiTransport('KEY'))->setHost('example.com')->setPort(99),
+                'postmark+api://example.com:99',
+            ],
+        ];
+    }
+}
diff --git a/src/Symfony/Component/Mailer/Bridge/Postmark/Tests/Transport/PostmarkTransportFactoryTest.php b/src/Symfony/Component/Mailer/Bridge/Postmark/Tests/Transport/PostmarkTransportFactoryTest.php
index 721af087a74d..d93a1a2081bb 100644
--- a/src/Symfony/Component/Mailer/Bridge/Postmark/Tests/Transport/PostmarkTransportFactoryTest.php
+++ b/src/Symfony/Component/Mailer/Bridge/Postmark/Tests/Transport/PostmarkTransportFactoryTest.php
@@ -28,23 +28,28 @@ public function getFactory(): TransportFactoryInterface
     public function supportsProvider(): iterable
     {
         yield [
-            new Dsn('api', 'postmark'),
+            new Dsn('postmark+api', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtp', 'postmark'),
+            new Dsn('postmark', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtps', 'postmark'),
+            new Dsn('postmark+smtp', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtp', 'example.com'),
-            false,
+            new Dsn('postmark+smtps', 'default'),
+            true,
+        ];
+
+        yield [
+            new Dsn('postmark+smtp', 'example.com'),
+            true,
         ];
     }
 
@@ -54,17 +59,27 @@ public function createProvider(): iterable
         $logger = $this->getLogger();
 
         yield [
-            new Dsn('api', 'postmark', self::USER),
+            new Dsn('postmark+api', 'default', self::USER),
             new PostmarkApiTransport(self::USER, $this->getClient(), $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('smtp', 'postmark', self::USER),
+            new Dsn('postmark+api', 'example.com', self::USER, '', 8080),
+            (new PostmarkApiTransport(self::USER, $this->getClient(), $dispatcher, $logger))->setHost('example.com')->setPort(8080),
+        ];
+
+        yield [
+            new Dsn('postmark', 'default', self::USER),
+            new PostmarkSmtpTransport(self::USER, $dispatcher, $logger),
+        ];
+
+        yield [
+            new Dsn('postmark+smtp', 'default', self::USER),
             new PostmarkSmtpTransport(self::USER, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('smtps', 'postmark', self::USER),
+            new Dsn('postmark+smtps', 'default', self::USER),
             new PostmarkSmtpTransport(self::USER, $dispatcher, $logger),
         ];
     }
@@ -72,13 +87,13 @@ public function createProvider(): iterable
     public function unsupportedSchemeProvider(): iterable
     {
         yield [
-            new Dsn('foo', 'postmark', self::USER),
-            'The "foo" scheme is not supported for mailer "postmark". Supported schemes are: "api", "smtp", "smtps".',
+            new Dsn('postmark+foo', 'default', self::USER),
+            'The "postmark+foo" scheme is not supported. Supported schemes for mailer "postmark" are: "postmark", "postmark+api", "postmark+smtp", "postmark+smtps".',
         ];
     }
 
     public function incompleteDsnProvider(): iterable
     {
-        yield [new Dsn('api', 'postmark')];
+        yield [new Dsn('postmark+api', 'default')];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkApiTransport.php b/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkApiTransport.php
index a13e8ae7300c..d7b8344c6b68 100644
--- a/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkApiTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkApiTransport.php
@@ -25,7 +25,7 @@
  */
 class PostmarkApiTransport extends AbstractApiTransport
 {
-    private const ENDPOINT = 'http://api.postmarkapp.com/email';
+    private const HOST = 'api.postmarkapp.com';
 
     private $key;
 
@@ -38,12 +38,12 @@ public function __construct(string $key, HttpClientInterface $client = null, Eve
 
     public function __toString(): string
     {
-        return sprintf('api://postmark');
+        return sprintf('postmark+api://%s', $this->getEndpoint());
     }
 
     protected function doSendApi(Email $email, SmtpEnvelope $envelope): ResponseInterface
     {
-        $response = $this->client->request('POST', self::ENDPOINT, [
+        $response = $this->client->request('POST', 'https://'.$this->getEndpoint().'/email', [
             'headers' => [
                 'Accept' => 'application/json',
                 'X-Postmark-Server-Token' => $this->key,
@@ -111,4 +111,9 @@ private function getAttachments(Email $email): array
 
         return $attachments;
     }
+
+    private function getEndpoint(): ?string
+    {
+        return ($this->host ?: self::HOST).($this->port ? ':'.$this->port : '');
+    }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkTransportFactory.php b/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkTransportFactory.php
index fbe6add0c287..983f41a4503e 100644
--- a/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkTransportFactory.php
+++ b/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkTransportFactory.php
@@ -26,19 +26,22 @@ public function create(Dsn $dsn): TransportInterface
         $scheme = $dsn->getScheme();
         $user = $this->getUser($dsn);
 
-        if ('api' === $scheme) {
-            return new PostmarkApiTransport($user, $this->client, $this->dispatcher, $this->logger);
+        if ('postmark+api' === $scheme) {
+            $host = 'default' === $dsn->getHost() ? null : $dsn->getHost();
+            $port = $dsn->getPort();
+
+            return (new PostmarkApiTransport($user, $this->client, $this->dispatcher, $this->logger))->setHost($host)->setPort($port);
         }
 
-        if ('smtp' === $scheme || 'smtps' === $scheme) {
+        if ('postmark+smtp' === $scheme || 'postmark+smtps' === $scheme || 'postmark' === $scheme) {
             return new PostmarkSmtpTransport($user, $this->dispatcher, $this->logger);
         }
 
-        throw new UnsupportedSchemeException($dsn, ['api', 'smtp', 'smtps']);
+        throw new UnsupportedSchemeException($dsn, 'postmark', $this->getSupportedSchemes());
     }
 
-    public function supports(Dsn $dsn): bool
+    protected function getSupportedSchemes(): array
     {
-        return 'postmark' === $dsn->getHost();
+        return ['postmark', 'postmark+api', 'postmark+smtp', 'postmark+smtps'];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Sendgrid/Tests/Transport/SendgridApiTransportTest.php b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Tests/Transport/SendgridApiTransportTest.php
index 083c04d3173d..ea5e91af1a94 100644
--- a/src/Symfony/Component/Mailer/Bridge/Sendgrid/Tests/Transport/SendgridApiTransportTest.php
+++ b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Tests/Transport/SendgridApiTransportTest.php
@@ -19,6 +19,32 @@
 
 class SendgridApiTransportTest extends TestCase
 {
+    /**
+     * @dataProvider getTransportData
+     */
+    public function testToString(SendgridApiTransport $transport, string $expected)
+    {
+        $this->assertSame($expected, (string) $transport);
+    }
+
+    public function getTransportData()
+    {
+        return [
+            [
+                new SendgridApiTransport('KEY'),
+                'sendgrid+api://api.sendgrid.com',
+            ],
+            [
+                (new SendgridApiTransport('KEY'))->setHost('example.com'),
+                'sendgrid+api://example.com',
+            ],
+            [
+                (new SendgridApiTransport('KEY'))->setHost('example.com')->setPort(99),
+                'sendgrid+api://example.com:99',
+            ],
+        ];
+    }
+
     public function testSend()
     {
         $email = new Email();
diff --git a/src/Symfony/Component/Mailer/Bridge/Sendgrid/Tests/Transport/SendgridTransportFactoryTest.php b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Tests/Transport/SendgridTransportFactoryTest.php
index e6494649cda6..b32c37e0c8b4 100644
--- a/src/Symfony/Component/Mailer/Bridge/Sendgrid/Tests/Transport/SendgridTransportFactoryTest.php
+++ b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Tests/Transport/SendgridTransportFactoryTest.php
@@ -28,23 +28,28 @@ public function getFactory(): TransportFactoryInterface
     public function supportsProvider(): iterable
     {
         yield [
-            new Dsn('api', 'sendgrid'),
+            new Dsn('sendgrid+api', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtp', 'sendgrid'),
+            new Dsn('sendgrid', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtps', 'sendgrid'),
+            new Dsn('sendgrid+smtp', 'default'),
             true,
         ];
 
         yield [
-            new Dsn('smtp', 'example.com'),
-            false,
+            new Dsn('sendgrid+smtps', 'default'),
+            true,
+        ];
+
+        yield [
+            new Dsn('sendgrid+smtp', 'example.com'),
+            true,
         ];
     }
 
@@ -54,17 +59,27 @@ public function createProvider(): iterable
         $logger = $this->getLogger();
 
         yield [
-            new Dsn('api', 'sendgrid', self::USER),
+            new Dsn('sendgrid+api', 'default', self::USER),
             new SendgridApiTransport(self::USER, $this->getClient(), $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('smtp', 'sendgrid', self::USER),
+            new Dsn('sendgrid+api', 'example.com', self::USER, '', 8080),
+            (new SendgridApiTransport(self::USER, $this->getClient(), $dispatcher, $logger))->setHost('example.com')->setPort(8080),
+        ];
+
+        yield [
+            new Dsn('sendgrid', 'default', self::USER),
+            new SendgridSmtpTransport(self::USER, $dispatcher, $logger),
+        ];
+
+        yield [
+            new Dsn('sendgrid+smtp', 'default', self::USER),
             new SendgridSmtpTransport(self::USER, $dispatcher, $logger),
         ];
 
         yield [
-            new Dsn('smtps', 'sendgrid', self::USER),
+            new Dsn('sendgrid+smtps', 'default', self::USER),
             new SendgridSmtpTransport(self::USER, $dispatcher, $logger),
         ];
     }
@@ -72,13 +87,13 @@ public function createProvider(): iterable
     public function unsupportedSchemeProvider(): iterable
     {
         yield [
-            new Dsn('foo', 'sendgrid', self::USER),
-            'The "foo" scheme is not supported for mailer "sendgrid". Supported schemes are: "api", "smtp", "smtps".',
+            new Dsn('sendgrid+foo', 'sendgrid', self::USER),
+            'The "sendgrid+foo" scheme is not supported. Supported schemes for mailer "sendgrid" are: "sendgrid", "sendgrid+api", "sendgrid+smtp", "sendgrid+smtps".',
         ];
     }
 
     public function incompleteDsnProvider(): iterable
     {
-        yield [new Dsn('api', 'sendgrid')];
+        yield [new Dsn('sendgrid+api', 'default')];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridApiTransport.php b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridApiTransport.php
index 8536b8eb6ce4..c945d96de9af 100644
--- a/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridApiTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridApiTransport.php
@@ -26,7 +26,7 @@
  */
 class SendgridApiTransport extends AbstractApiTransport
 {
-    private const ENDPOINT = 'https://api.sendgrid.com/v3/mail/send';
+    private const HOST = 'api.sendgrid.com';
 
     private $key;
 
@@ -39,12 +39,12 @@ public function __construct(string $key, HttpClientInterface $client = null, Eve
 
     public function __toString(): string
     {
-        return sprintf('api://sendgrid');
+        return sprintf('sendgrid+api://%s', $this->getEndpoint());
     }
 
     protected function doSendApi(Email $email, SmtpEnvelope $envelope): ResponseInterface
     {
-        $response = $this->client->request('POST', self::ENDPOINT, [
+        $response = $this->client->request('POST', 'https://'.$this->getEndpoint().'/v3/mail/send', [
             'json' => $this->getPayload($email, $envelope),
             'auth_bearer' => $this->key,
         ]);
@@ -136,4 +136,9 @@ private function getAttachments(Email $email): array
 
         return $attachments;
     }
+
+    private function getEndpoint(): ?string
+    {
+        return ($this->host ?: self::HOST).($this->port ? ':'.$this->port : '');
+    }
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridTransportFactory.php b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridTransportFactory.php
index 70d87a08dabf..a4734c7213d7 100644
--- a/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridTransportFactory.php
+++ b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridTransportFactory.php
@@ -25,19 +25,22 @@ public function create(Dsn $dsn): TransportInterface
     {
         $key = $this->getUser($dsn);
 
-        if ('api' === $dsn->getScheme()) {
-            return new SendgridApiTransport($key, $this->client, $this->dispatcher, $this->logger);
+        if ('sendgrid+api' === $dsn->getScheme()) {
+            $host = 'default' === $dsn->getHost() ? null : $dsn->getHost();
+            $port = $dsn->getPort();
+
+            return (new SendgridApiTransport($key, $this->client, $this->dispatcher, $this->logger))->setHost($host)->setPort($port);
         }
 
-        if ('smtp' === $dsn->getScheme() || 'smtps' === $dsn->getScheme()) {
+        if ('sendgrid+smtp' === $dsn->getScheme() || 'sendgrid+smtps' === $dsn->getScheme() || 'sendgrid' === $dsn->getScheme()) {
             return new SendgridSmtpTransport($key, $this->dispatcher, $this->logger);
         }
 
-        throw new UnsupportedSchemeException($dsn, ['api', 'smtp', 'smtps']);
+        throw new UnsupportedSchemeException($dsn, 'sendgrid', $this->getSupportedSchemes());
     }
 
-    public function supports(Dsn $dsn): bool
+    protected function getSupportedSchemes(): array
     {
-        return 'sendgrid' === $dsn->getHost();
+        return ['sendgrid', 'sendgrid+api', 'sendgrid+smtp', 'sendgrid+smtps'];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Exception/UnsupportedSchemeException.php b/src/Symfony/Component/Mailer/Exception/UnsupportedSchemeException.php
index e67733630cea..165d644cb301 100644
--- a/src/Symfony/Component/Mailer/Exception/UnsupportedSchemeException.php
+++ b/src/Symfony/Component/Mailer/Exception/UnsupportedSchemeException.php
@@ -18,8 +18,8 @@
  */
 class UnsupportedSchemeException extends LogicException
 {
-    public function __construct(Dsn $dsn, array $supported)
+    public function __construct(Dsn $dsn, string $name, array $supported)
     {
-        parent::__construct(sprintf('The "%s" scheme is not supported for mailer "%s". Supported schemes are: "%s".', $dsn->getScheme(), $dsn->getHost(), implode('", "', $supported)));
+        parent::__construct(sprintf('The "%s" scheme is not supported. Supported schemes for mailer "%s" are: "%s".', $dsn->getScheme(), $name, implode('", "', $supported)));
     }
 }
diff --git a/src/Symfony/Component/Mailer/Test/TransportFactoryTestCase.php b/src/Symfony/Component/Mailer/Test/TransportFactoryTestCase.php
index 6c73354bb385..34a264be7d6b 100644
--- a/src/Symfony/Component/Mailer/Test/TransportFactoryTestCase.php
+++ b/src/Symfony/Component/Mailer/Test/TransportFactoryTestCase.php
@@ -69,7 +69,7 @@ public function testCreate(Dsn $dsn, TransportInterface $transport): void
         $factory = $this->getFactory();
 
         $this->assertEquals($transport, $factory->create($dsn));
-        if ('smtp' !== $dsn->getScheme() && 'smtps' !== $dsn->getScheme()) {
+        if (false !== strpos('smtp', $dsn->getScheme())) {
             $this->assertStringMatchesFormat($dsn->getScheme().'://%S'.$dsn->getHost().'%S', (string) $transport);
         }
     }
diff --git a/src/Symfony/Component/Mailer/Tests/Transport/NullTransportFactoryTest.php b/src/Symfony/Component/Mailer/Tests/Transport/NullTransportFactoryTest.php
index 06248f34b51c..9b39a6140b6c 100644
--- a/src/Symfony/Component/Mailer/Tests/Transport/NullTransportFactoryTest.php
+++ b/src/Symfony/Component/Mailer/Tests/Transport/NullTransportFactoryTest.php
@@ -27,29 +27,16 @@ public function getFactory(): TransportFactoryInterface
     public function supportsProvider(): iterable
     {
         yield [
-            new Dsn('smtp', 'null'),
+            new Dsn('null', ''),
             true,
         ];
-
-        yield [
-            new Dsn('smtp', 'example.com'),
-            false,
-        ];
     }
 
     public function createProvider(): iterable
     {
         yield [
-            new Dsn('smtp', 'null'),
+            new Dsn('null', 'null'),
             new NullTransport($this->getDispatcher(), $this->getLogger()),
         ];
     }
-
-    public function unsupportedSchemeProvider(): iterable
-    {
-        yield [
-            new Dsn('foo', 'null'),
-            'The "foo" scheme is not supported for mailer "null". Supported schemes are: "smtp".',
-        ];
-    }
 }
diff --git a/src/Symfony/Component/Mailer/Tests/Transport/NullTransportTest.php b/src/Symfony/Component/Mailer/Tests/Transport/NullTransportTest.php
index c43bf90f9951..34c2a41392b1 100644
--- a/src/Symfony/Component/Mailer/Tests/Transport/NullTransportTest.php
+++ b/src/Symfony/Component/Mailer/Tests/Transport/NullTransportTest.php
@@ -19,6 +19,6 @@ class NullTransportTest extends TestCase
     public function testToString()
     {
         $t = new NullTransport();
-        $this->assertEquals('smtp://null', (string) $t);
+        $this->assertEquals('null://', (string) $t);
     }
 }
diff --git a/src/Symfony/Component/Mailer/Tests/Transport/SendmailTransportFactoryTest.php b/src/Symfony/Component/Mailer/Tests/Transport/SendmailTransportFactoryTest.php
index 84d8d92ca74a..078b00b6f5b5 100644
--- a/src/Symfony/Component/Mailer/Tests/Transport/SendmailTransportFactoryTest.php
+++ b/src/Symfony/Component/Mailer/Tests/Transport/SendmailTransportFactoryTest.php
@@ -27,20 +27,15 @@ public function getFactory(): TransportFactoryInterface
     public function supportsProvider(): iterable
     {
         yield [
-            new Dsn('smtp', 'sendmail'),
+            new Dsn('sendmail+smtp', 'default'),
             true,
         ];
-
-        yield [
-            new Dsn('smtp', 'example.com'),
-            false,
-        ];
     }
 
     public function createProvider(): iterable
     {
         yield [
-            new Dsn('smtp', 'sendmail'),
+            new Dsn('sendmail+smtp', 'default'),
             new SendmailTransport(null, $this->getDispatcher(), $this->getLogger()),
         ];
     }
@@ -48,8 +43,8 @@ public function createProvider(): iterable
     public function unsupportedSchemeProvider(): iterable
     {
         yield [
-            new Dsn('http', 'sendmail'),
-            'The "http" scheme is not supported for mailer "sendmail". Supported schemes are: "smtp".',
+            new Dsn('sendmail+http', 'default'),
+            'The "sendmail+http" scheme is not supported. Supported schemes for mailer "sendmail" are: "sendmail", "sendmail+smtp".',
         ];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Tests/Transport/Smtp/EsmtpTransportFactoryTest.php b/src/Symfony/Component/Mailer/Tests/Transport/Smtp/EsmtpTransportFactoryTest.php
index a3b13b624c42..7dcea33e9648 100644
--- a/src/Symfony/Component/Mailer/Tests/Transport/Smtp/EsmtpTransportFactoryTest.php
+++ b/src/Symfony/Component/Mailer/Tests/Transport/Smtp/EsmtpTransportFactoryTest.php
@@ -64,7 +64,7 @@ public function createProvider(): iterable
         $transport = new EsmtpTransport('example.com', 465, true, $eventDispatcher, $logger);
 
         yield [
-            new Dsn('smtp', 'example.com', '', '', 465),
+            new Dsn('smtps', 'example.com', '', '', 465),
             $transport,
         ];
     }
diff --git a/src/Symfony/Component/Mailer/Transport/AbstractHttpTransport.php b/src/Symfony/Component/Mailer/Transport/AbstractHttpTransport.php
index 17deb9fe614c..5480810b0d37 100644
--- a/src/Symfony/Component/Mailer/Transport/AbstractHttpTransport.php
+++ b/src/Symfony/Component/Mailer/Transport/AbstractHttpTransport.php
@@ -24,6 +24,8 @@
  */
 abstract class AbstractHttpTransport extends AbstractTransport
 {
+    protected $host;
+    protected $port;
     protected $client;
 
     public function __construct(HttpClientInterface $client = null, EventDispatcherInterface $dispatcher = null, LoggerInterface $logger = null)
@@ -40,6 +42,26 @@ public function __construct(HttpClientInterface $client = null, EventDispatcherI
         parent::__construct($dispatcher, $logger);
     }
 
+    /**
+     * @return $this
+     */
+    public function setHost(?string $host)
+    {
+        $this->host = $host;
+
+        return $this;
+    }
+
+    /**
+     * @return $this
+     */
+    public function setPort(?int $port)
+    {
+        $this->port = $port;
+
+        return $this;
+    }
+
     abstract protected function doSendHttp(SentMessage $message): ResponseInterface;
 
     protected function doSend(SentMessage $message): void
diff --git a/src/Symfony/Component/Mailer/Transport/AbstractTransportFactory.php b/src/Symfony/Component/Mailer/Transport/AbstractTransportFactory.php
index 959fca574660..17c87224df4a 100644
--- a/src/Symfony/Component/Mailer/Transport/AbstractTransportFactory.php
+++ b/src/Symfony/Component/Mailer/Transport/AbstractTransportFactory.php
@@ -32,6 +32,13 @@ public function __construct(EventDispatcherInterface $dispatcher = null, HttpCli
         $this->logger = $logger;
     }
 
+    public function supports(Dsn $dsn): bool
+    {
+        return \in_array($dsn->getScheme(), $this->getSupportedSchemes());
+    }
+
+    abstract protected function getSupportedSchemes(): array;
+
     protected function getUser(Dsn $dsn): string
     {
         $user = $dsn->getUser();
diff --git a/src/Symfony/Component/Mailer/Transport/NullTransport.php b/src/Symfony/Component/Mailer/Transport/NullTransport.php
index 71a0958b53d6..92fb82a478cb 100644
--- a/src/Symfony/Component/Mailer/Transport/NullTransport.php
+++ b/src/Symfony/Component/Mailer/Transport/NullTransport.php
@@ -26,6 +26,6 @@ protected function doSend(SentMessage $message): void
 
     public function __toString(): string
     {
-        return 'smtp://null';
+        return 'null://';
     }
 }
diff --git a/src/Symfony/Component/Mailer/Transport/NullTransportFactory.php b/src/Symfony/Component/Mailer/Transport/NullTransportFactory.php
index d874e5b583c4..4c45f39e1197 100644
--- a/src/Symfony/Component/Mailer/Transport/NullTransportFactory.php
+++ b/src/Symfony/Component/Mailer/Transport/NullTransportFactory.php
@@ -20,15 +20,15 @@ final class NullTransportFactory extends AbstractTransportFactory
 {
     public function create(Dsn $dsn): TransportInterface
     {
-        if ('smtp' === $dsn->getScheme()) {
+        if ('null' === $dsn->getScheme()) {
             return new NullTransport($this->dispatcher, $this->logger);
         }
 
-        throw new UnsupportedSchemeException($dsn, ['smtp']);
+        throw new UnsupportedSchemeException($dsn, 'null', $this->getSupportedSchemes());
     }
 
-    public function supports(Dsn $dsn): bool
+    protected function getSupportedSchemes(): array
     {
-        return 'null' === $dsn->getHost();
+        return ['null'];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Transport/SendmailTransportFactory.php b/src/Symfony/Component/Mailer/Transport/SendmailTransportFactory.php
index 5e89a2070e06..77d6d49a4a46 100644
--- a/src/Symfony/Component/Mailer/Transport/SendmailTransportFactory.php
+++ b/src/Symfony/Component/Mailer/Transport/SendmailTransportFactory.php
@@ -20,15 +20,15 @@ final class SendmailTransportFactory extends AbstractTransportFactory
 {
     public function create(Dsn $dsn): TransportInterface
     {
-        if ('smtp' === $dsn->getScheme()) {
+        if ('sendmail+smtp' === $dsn->getScheme() || 'sendmail' === $dsn->getScheme()) {
             return new SendmailTransport(null, $this->dispatcher, $this->logger);
         }
 
-        throw new UnsupportedSchemeException($dsn, ['smtp']);
+        throw new UnsupportedSchemeException($dsn, 'sendmail', $this->getSupportedSchemes());
     }
 
-    public function supports(Dsn $dsn): bool
+    protected function getSupportedSchemes(): array
     {
-        return 'sendmail' === $dsn->getHost();
+        return ['sendmail', 'sendmail+smtp'];
     }
 }
diff --git a/src/Symfony/Component/Mailer/Transport/Smtp/EsmtpTransportFactory.php b/src/Symfony/Component/Mailer/Transport/Smtp/EsmtpTransportFactory.php
index a1438f91f49f..6613145f68f8 100644
--- a/src/Symfony/Component/Mailer/Transport/Smtp/EsmtpTransportFactory.php
+++ b/src/Symfony/Component/Mailer/Transport/Smtp/EsmtpTransportFactory.php
@@ -39,8 +39,8 @@ public function create(Dsn $dsn): TransportInterface
         return $transport;
     }
 
-    public function supports(Dsn $dsn): bool
+    protected function getSupportedSchemes(): array
     {
-        return 'smtp' === $dsn->getScheme() || 'smtps' === $dsn->getScheme();
+        return ['smtp', 'smtps'];
     }
 }