The best way to send emails in Go with SMTP Keep Alive and Timeout for Connect and Send.
Examples in this README are for v2.2.0 and above. Examples for older versions can be found here.
The minimum Go version is 1.13, for Go 1.12 and older use branch go1.12.
Breaking change in 2.2.0: The signature of SetBody and AddAlternative used
to accept strings ("text/html" and "text/plain") and not require on of the
contentType constants (TextHTML or TextPlain). Upgrading, while not
quite following semantic versioning, is quite simple:
email := mail.NewMSG()
- email.SetBody("text/html", htmlBody)
- email.AddAlternative("text/plain", plainBody)
+ email.SetBody(mail.TextHTML, htmlBody)
+ email.AddAlternative(mail.TextPlain, plainBody)Go Simple Mail is a simple and efficient package to send emails. It is well tested and documented.
Go Simple Mail can only send emails using an SMTP server. But the API is flexible and it is easy to implement other methods for sending emails using a local Postfix, an API, etc.
This package contains (and is based on) two packages by Joe Grasse:
- https://github.com/joegrasse/mail (unmaintained since Jun 29, 2018), and
- https://github.com/joegrasse/mime (unmaintained since Oct 1, 2015).
A lot of changes in Go Simple Mail were sent with not response.
Go Simple Mail supports:
- Multiple Attachments with path
- Multiple Attachments in base64
- Multiple Recipients
- Priority
- Reply to
- Set other sender
- Set other from
- Embedded images
- HTML and text templates
- Automatic encoding of special characters
- SSL and TLS
- Unencrypted connection (not recommended)
- Sending multiple emails with the same SMTP connection (Keep Alive or Persistent Connection)
- Timeout for connect to a SMTP Server
- Timeout for send an email
- Return Path
- Alternative Email Body
- CC and BCC
- Add Custom Headers in Message
- Send NOOP, RESET, QUIT and CLOSE to SMTP client
- PLAIN, LOGIN and CRAM-MD5 Authentication (since v2.3.0)
- Custom TLS Configuration (since v2.5.0)
https://pkg.go.dev/github.com/xhit/go-simple-mail/v2?tab=doc
This package uses go modules.
$ go get github.com/xhit/go-simple-mail/v2package main
import (
"log"
"github.com/xhit/go-simple-mail/v2"
)
const htmlBody = `<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Hello Gophers!</title>
</head>
<body>
<p>This is the <b>Go gopher</b>.</p>
<p><img src="cid:Gopher.png" alt="Go gopher" /></p>
<p>Image created by Renee French</p>
</body>
</html>`
func main() {
server := mail.NewSMTPClient()
// SMTP Server
server.Host = "smtp.example.com"
server.Port = 587
server.Username = "test@example.com"
server.Password = "examplepass"
server.Encryption = mail.EncryptionTLS
// Since v2.3.0 you can specified authentication type:
// - PLAIN (default)
// - LOGIN
// - CRAM-MD5
// server.Authentication = mail.AuthPlain
// Variable to keep alive connection
server.KeepAlive = false
// Timeout for connect to SMTP Server
server.ConnectTimeout = 10 * time.Second
// Timeout for send the data and wait respond
server.SendTimeout = 10 * time.Second
// Set TLSConfig to provide custom TLS configuration. For example,
// to skip TLS verification (useful for testing):
server.TLSConfig = &tls.Config{InsecureSkipVerify: true}
// SMTP client
smtpClient,err := server.Connect()
if err != nil{
log.Fatal(err)
}
// New email simple html with inline and CC
email := mail.NewMSG()
email.SetFrom("From Example <nube@example.com>").
AddTo("xhit@example.com").
AddCc("otherto@example.com").
SetSubject("New Go Email")
email.SetBody(mail.TextHTML, htmlBody)
email.AddInline("/path/to/image.png", "Gopher.png")
// Call Send and pass the client
err = email.Send(smtpClient)
if err != nil {
log.Println(err)
} else {
log.Println("Email Sent")
}
} //Set your smtpClient struct to keep alive connection
server.KeepAlive = true
for _, to := range []string{
"to1@example1.com",
"to3@example2.com",
"to4@example3.com",
} {
// New email simple html with inline and CC
email := mail.NewMSG()
email.SetFrom("From Example <nube@example.com>").
AddTo(to).
SetSubject("New Go Email")
email.SetBody(mail.TextHTML, htmlBody)
email.AddInline("/path/to/image.png", "Gopher.png")
// Call Send and pass the client
err = email.Send(smtpClient)
if err != nil {
log.Println(err)
} else {
log.Println("Email Sent")
}
}