============= Posting loops ============= 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