diff --git a/scrapy/mail.py b/scrapy/mail.py
index 7365f25b7..7f237820f 100644
--- a/scrapy/mail.py
+++ b/scrapy/mail.py
@@ -5,10 +5,13 @@ See documentation in docs/topics/email.rst
 """
 import logging
 
+try:
+    from cStringIO import StringIO as BytesIO
+except ImportError:
+    from io import BytesIO
 import six
 
 from email.utils import COMMASPACE, formatdate
-from io import BytesIO
 from six.moves.email_mime_multipart import MIMEMultipart
 from six.moves.email_mime_text import MIMEText
 from six.moves.email_mime_base import MIMEBase
@@ -21,14 +24,6 @@ else:
 
 from twisted.internet import defer, reactor, ssl
 
-try:
-    from twisted.mail.smtp import ESMTPSenderFactory
-except ImportError:
-    """
-    twisted.mail.smtp was not available in
-    older versions of Twisted on Python 3
-    """
-
 from .utils.misc import arg_to_iter
 
 logger = logging.getLogger(__name__)
@@ -96,7 +91,7 @@ class MailSender(object):
                           'mailattachs': len(attachs)})
             return
 
-        dfd = self._sendmail(rcpts, msg.as_string())
+        dfd = self._sendmail(rcpts, msg.as_string().encode(charset or 'utf-8'))
         dfd.addCallbacks(self._sent_ok, self._sent_failed,
             callbackArgs=[to, cc, subject, len(attachs)],
             errbackArgs=[to, cc, subject, len(attachs)])
@@ -118,7 +113,9 @@ class MailSender(object):
                       'mailattachs': nattachs, 'mailerr': errstr})
 
     def _sendmail(self, to_addrs, msg):
-        msg = BytesIO(msg.encode('utf-8'))
+        # Import twisted.mail here because it is not available in python3
+        from twisted.mail.smtp import ESMTPSenderFactory
+        msg = BytesIO(msg)
         d = defer.Deferred()
         factory = ESMTPSenderFactory(self.smtpuser, self.smtppass, self.mailfrom, \
             to_addrs, msg, d, heloFallback=True, requireAuthentication=False, \