# SMTP authentication

The SMTP server may require authentication. Mailman supports setting the SMTP user name and password. The actual authentication mechanism used is determined by Python’s smtplib module, which tries the more secure CRAM-MD5 method first, followed by the less secure mechanisms PLAIN and LOGIN.

When sending authentication data between Mailman and the MTA over an unsecured network, the submission (mail) server should offer CRAM-MD5 as mechanism to have Python’s smtplib module automatically choose the more secure mechanism.

When the user name and password match what’s expected by the server, everything is a-okay.

    >>> mlist = create_list('test@example.com')

By default there is no user name and password, but this matches what’s expected by the test server.

    >>> config.push('auth', """
    ... [mta]
    ... smtp_user: testuser
    ... smtp_pass: testpass
    ... """)

Attempting delivery first must authorize with the mail server.

    >>> from mailman.mta.bulk import BulkDelivery
    >>> bulk = BulkDelivery()

    >>> msg = message_from_string("""\
    ... From: aperson@example.com
    ... To: test@example.com
    ... Subject: My first post
    ... Message-ID: <first>
    ...
    ... First post!
    ... """)

    >>> bulk.deliver(mlist, msg, dict(recipients=['bperson@example.com']))
    {}

    >>> print(smtpd.get_authentication_credentials())
    AHRlc3R1c2VyAHRlc3RwYXNz
    >>> config.pop('auth')

But if the user name and password does not match, the connection will fail.

    >>> config.push('auth', """
    ... [mta]
    ... smtp_user: baduser
    ... smtp_pass: badpass
    ... """)

    >>> bulk = BulkDelivery()
    >>> response = bulk.deliver(
    ...     mlist, msg, dict(recipients=['bperson@example.com']))
    >>> dump_msgdata(response)
    bperson@example.com: (571, b'Bad authentication')

    >>> config.pop('auth')