A considerable number of list subscribers' mail servers rejected today's two
postings from "tao", complaining about the mail header not being RFC 2822
compliant. Apparently the error was that the To: field
contained "exim-users@???." (note the explicit root domain final dot).
Indeed this is a syntax error (despite the fact that including that dot is
generally allowed), but I thought I'd make you aware that strict syntax
checking might be too, well, strict, and cause false positives (and strong
language such as "Header syntax of YOUR e-mail is invalid! Go home, read RFC
2822 carefully and check YOUR mail!" might be a bit too abusive).
I haven't checked whether any or all of the MTAs in question run Exim, but
another common false positive I've noticed when using verify = header_syntax
is addresses of the form "somebody@??? <somebody@???>",
which some MUAs generate when no display name is entered.
Speaking of dubious anti-spam measures, it also seems that some servers return
temporary status codes when they don't like the message content. It seems
like that because they consistently returns 45x after end of DATA for some
messages (or at connect, if they don't like the connecting host; Yahoo seems
to do this, for example), while accepting all other messages right away. If
it's not going to be accepted ever, a permanent status code should be
returned. The error messages don't always provide a specific reason, so it
might also be that some emails trigger some unexpected problem.
In any case, whitelisting 131.111.8.192 and other trustworthy mailing list
servers, if you can, should be a good idea. 99.9-100% of all spam that makes
it through to Mailman is held there, due to the sender being unknown, and
subsequently discarded by the moderators. Rejecting list mail not only means
that you miss it, but also that you risk being unsubscribed.
--
Magnus Holmgren holmgren@???
(No Cc of list mail needed, thanks)
