email modules and attachments that aren't there

[Russell Bungay]

Hello all,

I have written a short function, based on a recipe in the Python 
Cookbook, that sends an e-mail.  The function takes arguments that 
define who the e-mail is to, from, the subject, the body and an optional 
list of attachments.

The function works also perfectly, bar one slight problem.  If you 
attempt to send an e-mail with just a body and no attachments, the 
receiving client still thinks that there is an attachment (so far tested 
in Mozilla Thunderbird and the Yahoo! webmail client).  Although this 
clearly isn't a major problem, it is irritating and I am hoping to use 
my code at work.  Obviously I can't be sending out badly formed e-mails 
to my clients.

I can't for the life of me work out why.  I have compared my code to 
every example that I can find in the Python documentation, on the 
archives of this newsgroup and of the Python Tutor list, and one or two 
random searches but can't see what is happening.  Any advice or 
suggestions would be welcome.

Thank you for your help,

Russell Bungay
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Code:

def sendEmail(msg_to, msg_from, msg_subject, message, attachments=[]):

     main_msg = email.Message.Message()
     main_msg['To'] = ', '.join(msg_to)
     main_msg['From'] = msg_from
     main_msg['Subject'] = msg_subject
     main_msg['Date'] = email.Utils.formatdate(localtime=1)
     main_msg['Message-ID'] = email.Utils.make_msgid()
     main_msg['Mime-version'] = '1.0'
     main_msg['Content-type'] = 'Multipart/mixed'
     main_msg.preamble = 'Mime message\n'
     main_msg.epilogue = ''

     body_encoded = quopri.encodestring(message, 1)
     body_msg = email.Message.Message()
     body_msg.add_header('Content-type', 'text/plain')
     body_msg.add_header('Content-transfer-encoding', 'quoted-printable')
     body_msg.set_payload(body_encoded)
     main_msg.attach(body_msg)

     for attachment in attachments:

         content_type, ignored = mimetypes.guess_type(attachment)
         if content_type == None:
             content_type = 'application/octet-stream'
         contents_encoded = cStingIO.StringIO()
         attach_file = open(attachment, 'rb')
         main_type = content_type[:content_type.find('/')]
         if main_type == 'text':
             cte = 'quoted-printable'
             quopri.encode(attach_file, contents_encoded, 1)
         else:
             cte = 'base64'
             base64.encode(attach_file, contents_encoded)
         attach_file.close()

         sub_msg = email.Message.Message()
         sub_msg.add_header('Content-type', content_type, name=attachment)
         sub_msg.add_header('Content-transfer-encoding', cte)
         sub_msg.set_payload(contents_encoded.getvalue())
         main_msg.attach(sub_msg)

     smtp = smtplib.SMTP(server)
     smtpfail = smtp.sendmail(msg_from, ', '.join(msg_to), 
main_msg.as_string())
     smtp.quit()