Hi,Yesterday I implemented an ACL snippet that blocked all mail that did not have a Message-ID: header present. Today, I got a lot of complaints of customers who's mail bounced. Who would have guessed... ;-)
So I started reading up on the subject (should have done that before, but time is precious), but I couldn't get everything 100% clear.
One example of blocked mail came from a large internet provider in The Netherlands (@Home) that, according to the Received headers, uses Exim 4.30. This particular mail came from one of their clients and did not have a Message-ID header.
I have always thoughtlessly assumed that Exim would add a Message-ID header if missing, but this case led me to "control = submission". I immediately jumped to the conclusion that I needed something like:
warn hosts = +relay_from_hosts
control = submission
on all outgoing mail relays that are under my control.
However, a quick'n'dirty test with our Exim 4.50 here at the office
learns me that a Message-ID header /is/ added when I relay a mail
through it, even though there is no "control = submission" to be found
anywhere in the config.
I read that Exim's behaviour has changed over time in this respect. How should I look at this issue? What are recommended settings?
And a little off-topic:RFC2822 states a Message-ID header SHOULD be present in all mails, meaning it is not absolutely mandatory. How does the Exim community look at this? Should I try and persuade the mentioned provider to fix up messages from their clients?
Thanks, Martijn Grendelman.
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