Using Python's built-in smtplib to send files

sendfile.py

#!/usr/bin/env python

"""Script for sending an email (with an optional file attachment)."""

# Modified from the documentation at
# https://docs.python.org/2/library/email-examples.html
#
# Tested against python 2.6, 2.7 and 3.6
#
# For help, run this script!

import os
import sys
import smtplib
# For guessing MIME type based on file name extension
import mimetypes
import ssl

from optparse import OptionParser

from email import encoders
from email.mime.audio import MIMEAudio
from email.mime.base import MIMEBase
from email.mime.image import MIMEImage
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText

COMMASPACE = ', '


def main(args=sys.argv):
    parser = OptionParser(usage="""\
Send an email. Optionally, include a file attachment. The body will be
read from standard input, type <Enter>.<Enter> to end input.

Usage: %prog [options]

The email is sent by forwarding to your local SMTP server (running on
localhost), unless you specify either the -t or the -o option.
""")
    parser.add_option('-s', '--sender',
                      type='string', action='store', metavar='SENDER',
                      help='The value of the From: header (required)')
    parser.add_option('-r', '--recipient',
                      type='string', action='append', metavar='RECIPIENT',
                      default=[], dest='recipients',
                      help='A To: header value (at least one required)')
    parser.add_option('-u', '--subject',
                      type='string', action='store', metavar='SUBJECT',
                      help='The subject of the email. (required)')
    parser.add_option('-f', '--file',
                      type='string', action='store', metavar='INFILE',
                      help="""Send the specified file as an attachment.
                      (optional)""")
    parser.add_option('-t', '--smtp-host',
                      type='string', action='store', metavar='HOST',
                      help="""Use this smtp server to send mail, instead
                        of localhost. (optional)""")
    parser.add_option('-l', '--login-name',
                      type='string', action='store', metavar='USER',
                      help="""Username to authenticate to the SMTP
                      server. (optional)""")
    parser.add_option('-p', '--password',
                      type='string', action='store', metavar='PASSWORD',
                      help="""Password to authenticate to the SMTP
                      server. (optional)""")
    parser.add_option('--tls', default=False, action='store_true',
                      metavar='TLS', help="""Use TLS for connection""")
    parser.add_option('-o', '--output',
                      type='string', action='store', metavar='OUTFILE',
                      help="""Print the composed message to FILE instead of
                      sending the message to the SMTP server. (for
                      testing - optional)""")
    opts, args = parser.parse_args(args)
    if not opts.sender or not opts.recipients or not opts.subject:
        parser.print_help()
        sys.exit(1)

    msg = None
    if opts.file and os.path.isfile(opts.file):
        print("Adding file " + opts.file)
        # Guess the content type based on the file's extension.  Encoding
        # will be ignored, although we should check for simple things like
        # gzip'd or compressed files.
        ctype, encoding = mimetypes.guess_type(opts.file)
        if ctype is None or encoding is not None:
            # No guess could be made, or the file is encoded (compressed), so
            # use a generic bag-of-bits type.
            ctype = 'application/octet-stream'
        maintype, subtype = ctype.split('/', 1)
        if maintype == 'text':
            fp = open(opts.file)
            # Note: we should handle calculating the charset
            msg = MIMEText(fp.read(), _subtype=subtype)
            fp.close()
        elif maintype == 'image':
            fp = open(opts.file, 'rb')
            msg = MIMEImage(fp.read(), _subtype=subtype)
            fp.close()
        elif maintype == 'audio':
            fp = open(opts.file, 'rb')
            msg = MIMEAudio(fp.read(), _subtype=subtype)
            fp.close()
        else:
            fp = open(opts.file, 'rb')
            msg = MIMEBase(maintype, subtype)
            msg.set_payload(fp.read())
            fp.close()
            # Encode the payload using Base64
            encoders.encode_base64(msg)
        # Set the filename parameter
        # Use only the base filename, not the whole path
        fileparts = str(opts.file).split("/")
        filebase = fileparts[len(fileparts) - 1]
        msg.add_header('Content-Disposition', 'attachment', filename=filebase)

    # Get input from stdin
    lines = ""
    try:
        while 1:
            line = sys.stdin.readline()
            if not line or line == ".\n":
                break
            lines += line
    except (IOError, OSError):
        pass

    # Create the enclosing (outer) message
    outer = MIMEMultipart('mixed')
    outer['Subject'] = opts.subject
    outer['To'] = COMMASPACE.join(opts.recipients)
    outer['From'] = opts.sender

    # Add body
    if lines:
        body = MIMEText(lines, 'plain')
        outer.attach(body)
    else:
        print("Sending without a message body...\n")
    # Add attachment
    if msg is not None:
        outer.attach(msg)

    # Now send or store the message
    composed = outer.as_string()

    if opts.output:
        fp = open(opts.output, 'w')
        fp.write(composed)
        fp.close()
    else:
        host = opts.smtp_host if opts.smtp_host else 'localhost'

        # Create smtp object
        if opts.tls:
            s = smtplib.SMTP_SSL(host, timeout=5)
        else:
            s = smtplib.SMTP(host, timeout=5)
        # Login
        if opts.login_name and opts.password:
            s.login(opts.login_name, opts.password)
        # Send, then quit
        s.sendmail(opts.sender, opts.recipients, composed)
        s.quit()


if __name__ == '__main__':
    main()