Re: [exim] Header syntax checking

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Author: Mike Cardwell
Date:  
To: exim users
Subject: Re: [exim] Header syntax checking
Magnus Holmgren wrote:

> 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 tried strict header syntax checking a while back. I just set it to log
what it caught. It caught a *lot* of legit mail so I stopped. *maybe*
it'd be any extra 0.1 or 0.2 points in spamassassin but it's not a very
good idea to do an outright rejection on it.

> 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.


I suspect most people try to avoid maintaining their own local
whitelists of ip addresses. personally:

root@clayman:~# grep cam /etc/exim4/lists/whitelist-sender_host_name.txt
*.csx.cam.ac.uk

I'm semi tempted to just add:

accept condition = ${if match_domain{$sender_host_name}{*.ac.uk}}
        condition = ${if match{$sender_address_local_part}{-bounce}}


Mike