Posting loopsΒΆ

To avoid a posting loop, Mailman has a rule to check for the existence of an RFC 2369 List-Post: header with the value of the list’s posting address.

>>> mlist = create_list('_xtest@example.com')
>>> rule = config.rules['loop']
>>> print(rule.name)
loop

The header could be missing, in which case the rule does not match.

>>> msg = message_from_string("""\
... From: aperson@example.com
...
... An important message.
... """)
>>> rule.check(mlist, msg, {})
False

The header could be present, but not match the list’s posting address.

>>> msg['List-Post'] = 'not-this-list@example.com'
>>> rule.check(mlist, msg, {})
False

If the header is present and does match the posting address, the rule matches.

>>> del msg['list-post']
>>> msg['List-Post'] = mlist.posting_address
>>> rule.check(mlist, msg, {})
True

Even if there are multiple List-Post: headers, as long as one with the posting address exists, the rule matches.

>>> msg = message_from_string("""\
... From: aperson@example.com
... List-Post: not-this-list@example.com
... List-Post: _xtest@example.com
... List-Post: foo@example.com
...
... An important message.
... """)
>>> rule.check(mlist, msg, {})
True