Index: Lib/smtplib.py
===================================================================
--- Lib/smtplib.py	(revision 88500)
+++ Lib/smtplib.py	(working copy)
@@ -232,7 +232,8 @@
     does_esmtp = 0
 
     def __init__(self, host='', port=0, local_hostname=None,
-                 timeout=socket._GLOBAL_DEFAULT_TIMEOUT):
+                 timeout=socket._GLOBAL_DEFAULT_TIMEOUT, source_ip='',
+                 source_port=0):
         """Initialize a new instance.
 
         If specified, `host' is the name of the remote host to which to
@@ -242,12 +243,18 @@
         `local_hostname` is used as the FQDN of the local host.  By default,
         the local hostname is found using socket.getfqdn().
 
+        If `source_ip' and/or `source_port' are specified, the socket will bind
+        to this source IP address and/or port number before connecting. This is
+        useful in a system with multiple interfaces. When ommited, the behavior
+        will be according to the OS defaults.
         """
         self.timeout = timeout
         self.esmtp_features = {}
         self.default_port = SMTP_PORT
+        self.source_ip = source_ip
+        self.source_port = source_port
         if host:
-            (code, msg) = self.connect(host, port)
+            (code, msg) = self.connect(host, port, source_ip, source_port)
             if code != 220:
                 raise SMTPConnectError(code, msg)
         if local_hostname is not None:
@@ -277,13 +284,15 @@
         """
         self.debuglevel = debuglevel
 
-    def _get_socket(self, host, port, timeout):
+    def _get_socket(self, host, port, timeout, source_ip='', source_port=0):
         # This makes it simpler for SMTP_SSL to use the SMTP connect code
         # and just alter the socket connection bit.
-        if self.debuglevel > 0: print('connect:', (host, port), file=stderr)
-        return socket.create_connection((host, port), timeout)
+        if self.debuglevel > 0: print('connect: to', (host, port), 'from'
+                                      (source_ip, source_port), file=stderr)
+        return socket.create_connection((host, port), timeout,
+                                        (source_ip, source_port))
 
-    def connect(self, host='localhost', port = 0):
+    def connect(self, host='localhost', port = 0, source_ip='', source_port=0):
         """Connect to a host on a given port.
 
         If the hostname ends with a colon (`:') followed by a number, and
@@ -302,8 +311,11 @@
                 except ValueError:
                     raise socket.error("nonnumeric port")
         if not port: port = self.default_port
+        if self.source_ip and not source_ip: source_ip = self.source_ip
+        if self.source_port and not source_port: source_port = self.source_port
         if self.debuglevel > 0: print('connect:', (host, port), file=stderr)
-        self.sock = self._get_socket(host, port, self.timeout)
+        self.sock = self._get_socket(host, port, self.timeout, source_ip,
+                                     source_port)
         (code, msg) = self.getreply()
         if self.debuglevel > 0: print("connect:", msg, file=stderr)
         return (code, msg)
@@ -799,15 +811,19 @@
         """
         def __init__(self, host='', port=0, local_hostname=None,
                      keyfile=None, certfile=None,
-                     timeout=socket._GLOBAL_DEFAULT_TIMEOUT):
+                     timeout=socket._GLOBAL_DEFAULT_TIMEOUT,
+                     source_ip='', source_port=0):
             self.keyfile = keyfile
             self.certfile = certfile
-            SMTP.__init__(self, host, port, local_hostname, timeout)
+            SMTP.__init__(self, host, port, local_hostname, timeout, source_ip,
+                          source_port)
             self.default_port = SMTP_SSL_PORT
 
-        def _get_socket(self, host, port, timeout):
-            if self.debuglevel > 0: print('connect:', (host, port), file=stderr)
-            new_socket = socket.create_connection((host, port), timeout)
+        def _get_socket(self, host, port, timeout, source_ip='', source_port=0):
+            if self.debuglevel > 0: print('connect: to', (host, port), 'from'
+                                          (source_ip, source_port), file=stderr)
+            new_socket =  socket.create_connection((host, port), timeout,
+                                                   (source_ip, source_port))
             new_socket = ssl.wrap_socket(new_socket, self.keyfile, self.certfile)
             self.file = SSLFakeFile(new_socket)
             return new_socket
Index: Lib/test/test_smtplib.py
===================================================================
--- Lib/test/test_smtplib.py	(revision 88500)
+++ Lib/test/test_smtplib.py	(working copy)
@@ -78,6 +78,12 @@
         smtp = smtplib.SMTP("%s:%s" % (HOST, self.port))
         smtp.close()
 
+    def testSourceIPPort(self):
+        mock_socket.reply_with(b"220 Hola mundo")
+        smtp = smtplib.SMTP(HOST, self.port, source_ip='127.0.0.1',
+                            source_port=19876)
+        smtp.close()
+
     def testLocalHostName(self):
         mock_socket.reply_with(b"220 Hola mundo")
         # check that supplied local_hostname is used
@@ -206,6 +212,12 @@
         smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost', timeout=3)
         smtp.quit()
 
+    def testSourceIPPort(self):
+        # connect
+        smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost', timeout=3,
+                            source_ip='127.0.0.1', source_port=19876)
+        smtp.quit()
+
     def testNOOP(self):
         smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost', timeout=3)
         expected = (250, b'Ok')
Index: Lib/test/mock_socket.py
===================================================================
--- Lib/test/mock_socket.py	(revision 88500)
+++ Lib/test/mock_socket.py	(working copy)
@@ -106,7 +106,8 @@
     return MockSocket()
 
 
-def create_connection(address, timeout=socket_module._GLOBAL_DEFAULT_TIMEOUT):
+def create_connection(address, timeout=socket_module._GLOBAL_DEFAULT_TIMEOUT,
+                      source_address=None):
     try:
         int_port = int(address[1])
     except ValueError: