Re: [exim] Exim 4.77 and understanding DKIM signature verifi…

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Author: Ian Eiloart
To: Jeremy Harris
CC: <>
Subject: Re: [exim] Exim 4.77 and understanding DKIM signature verification and DKIM ACL
On 14 Apr 2012, at 23:15, Jeremy Harris wrote:
> On 2012-04-14 22:04, Michael J. Tubby B.Sc G8TIC wrote:
>> One of the conditions that I'm not sure how we resolve (or even it it ever happens) is what we do if there are two signatures on an incoming message and one is good (pass) and one is bad (fail) - but I guess this is down to the ACL creator ;-)
> I'm not a DKIM user myself, but I see plenty of mails through my system
> that are described exactly like that.....

That's quite a normal situation. Mailing lists tend to break DKIM signatures. However, it's recommended practice for a mailing list to add its own signature, and not remove the signature that it has just broken (e.g., by adding a footer to the message, or by adding a prefix to the Subject line).

The broken signature is not removed because it carries potentially useful information, even though that information cannot be relied upon.
Ian Eiloart
Postmaster, University of Sussex
+44 (0) 1273 87-3148