[9740] ESMTPSender: dont't force TLSv1.0 by default

src/twisted/mail/newsfragments/9740.bugfix

@@ -0,0 +1 @@
+twisted.mail.smtp.ESMTPSender no longer forces TLSv1.0 when used without explicit context factory.

src/twisted/mail/smtp.py

@@ -1196,7 +1196,7 @@ class ESMTPClient(SMTPClient):
     @type requireAuthentication: L{bool}
 
     @ivar context: The context factory to use for STARTTLS, if desired.
-    @type context: L{ssl.ClientContextFactory}
+    @type context: L{IOpenSSLClientConnectionCreator}
 
     @ivar _tlsMode: Whether or not the connection is over TLS.
     @type _tlsMode: L{bool}
@@ -2010,6 +2010,11 @@ def __init__(self, username, secret, contextFactory=None, *args, **kw):
         self.heloFallback = 0
         self.username = username
 
+        self._hostname = None
+        if 'hostname' in kw:
+            self._hostname = kw['hostname']
+            del kw['hostname']
+
         if contextFactory is None:
             contextFactory = self._getContextFactory()
 
@@ -2028,14 +2033,15 @@ def _registerAuthenticators(self):
     def _getContextFactory(self):
         if self.context is not None:
             return self.context
+        if self._hostname is None:
+            return None
         try:
-            from twisted.internet import ssl
+            from twisted.internet._sslverify import optionsForClientTLS
         except ImportError:
             return None
         else:
             try:
-                context = ssl.ClientContextFactory()
-                context.method = ssl.SSL.TLSv1_METHOD
+                context = optionsForClientTLS(self._hostname)
                 return context
             except AttributeError:
                 return None
@@ -2056,15 +2062,18 @@ def __init__(self, username, password, fromEmail, toEmail, file,
                  deferred, retries=5, timeout=None,
                  contextFactory=None, heloFallback=False,
                  requireAuthentication=True,
-                 requireTransportSecurity=True):
+                 requireTransportSecurity=True,
+                 hostname=None):
 
-        SMTPSenderFactory.__init__(self, fromEmail, toEmail, file, deferred, retries, timeout)
+        SMTPSenderFactory.__init__(self, fromEmail, toEmail, file, deferred,
+                                   retries, timeout)
         self.username = username
         self.password = password
         self._contextFactory = contextFactory
         self._heloFallback = heloFallback
         self._requireAuthentication = requireAuthentication
         self._requireTransportSecurity = requireTransportSecurity
+        self._hostname = hostname
 
 
     def buildProtocol(self, addr):
@@ -2078,7 +2087,8 @@ def buildProtocol(self, addr):
         @rtype: L{ESMTPSender}
         """
         p = self.protocol(self.username, self.password, self._contextFactory,
-                          self.domain, self.nEmails*2+2)
+                          self.domain, self.nEmails*2+2,
+                          hostname=self._hostname)
         p.heloFallback = self._heloFallback
         p.requireAuthentication = self._requireAuthentication
         p.requireTransportSecurity = self._requireTransportSecurity
@@ -2179,9 +2189,22 @@ def cancel(d):
     if isinstance(password, unicode):
         password = password.encode("utf-8")
 
-    factory = ESMTPSenderFactory(username, password, from_addr, to_addrs, msg,
-        d, heloFallback=True, requireAuthentication=requireAuthentication,
-        requireTransportSecurity=requireTransportSecurity)
+    tlsHostname = smtphost
+    if not isinstance(tlsHostname, unicode):
+        tlsHostname = tlsHostname.decode("ascii")
+
+    factory = ESMTPSenderFactory(
+        username,
+        password,
+        from_addr,
+        to_addrs,
+        msg,
+        d,
+        heloFallback=True,
+        requireAuthentication=requireAuthentication,
+        requireTransportSecurity=requireTransportSecurity,
+        hostname=tlsHostname
+    )
 
     if senderDomainName is not None:
         factory.domain = networkString(senderDomainName)