I have a number of lists that I administer that seem to have come across a nasty quirk. I use postfix and spamassassin to keep spam in check but recently I've noticed something different.

I disallow any posts coming in externally with @my_domain via postfix (it uses the envelope sender to do the checks). Mailman, on the other hand, uses the header From: field and thus the problem.

I've recently got mails that looks like this,

From him@outside.com Date: blah blah From: me@my_domain.com

so postfix processes it and allows it into my queues (after all it is not being spoofed - the envelope (first From) is clean). Mailman though sizes up this email based on the From: header field and denotes it a locally generate post which I allow irrespective of subscription (I have non-member filtering to allow posts from '.*@my_domain.com' through via the 'accept_these_nonmembers' setting).

So I have 2 questions,

1. Anyone know of a decent way to make sure that both the envelope sender and the noted From header field do in fact match ? else reject/discard the email.

2. Does mailman allow one to check the envelope sender instead of the From: header field ? That way I know both postfix and mailman are looking at the same thing.

I'm using postfix-2.0.16; question-1 above also needs to account for myself being able to mail out without issue (ie. in case someone suggests header filtering within postfix -- that would stop internal emails from going out and I'm unable to upgrade to postfix-2.1 just yet which seems to have hooks for this now).

Regards,

• Nadim

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