[Mailman-Users] OT - Smart .forward replacement?

Lindsay Haisley fmouse at fmp.com
Sun Nov 25 13:43:06 EST 2018

On Sun, 2018-11-25 at 00:17 -0500, Jayson Smith wrote:
> I've been using .forward to forward Email from some user mailboxes to 
> other addresses. Normally this works just fine, but a few weeks ago a 
> situation happened which demonstrates how it can be an epic fail. I had 
> a Mailman/DNS problem after upgrading a lot of packages.

How does a .forward problem relate to Mailman? Please excuse my
ignorance if this is obvious. I use Courier-MTA and the equivalent
facility is the .courier file, which redirects email. In the case of
Mailman mailing lists, I use the courier-to-mailman.py as a target in a
.courier file to redirect _internally_ into Mailman. Otherwise external
redirection in a .forward file (which is an ancient and venerable
sendmail facility) can (probably will) cause problems if the
redirection is from a "p=reject" domain to a service, such as Gmail,
which honors this.

> A message came 
> in, Mailman couldn't properly look up the DMARC policy of the sending 
> ISP, didn't munge the From: and sent the message on its way, and of 
> course the message was from AOL, just about everybody rejected it, I 
> woke up to fifty-five bounce reports…and all those bounce reports were 
> also forwarded to an Email account on an Internet by telephone service, 
> where deleting them was extremely slow.

Setting from_is_list to "Munge From" in General Options will apply
DMARC mitigation to _all_ From addresses. I believe this takes
precedence over dmarc_moderation_action which requires a DNS lookup of
the sender's DMARC policy.

It might be a good idea to use this setting preemptively any time you
make system changes (or may have problems) which may affect the ability
of Mailman to do a proper DNS lookup of a sender.s DMARC policy.

> What I'm looking for is possibly something that checks mailboxes from 
> time to time, and forwards all incoming messages that meet certain 
> parameters, taking care of DMARC difficulties along the way so the 
> forwarded messages will be accepted by the remote servers. E.G. my mom 
> uses that net by phone service, and would like to see Email which comes 
> to her regular Email address, but doesn't want to spend time deleting 
> Amazon order confirmations, Mailman moderation notices, and other 
> routine, automated, or irrelevant messages. Does such a thing exist?

Leaving from_is_list set to "Munge From" will take care of any DNS
outages, if you don't mind doing this. When it comes to specialized
software to do things such as scan mailboxes and take intelligent
action, I've found that I pretty much have to write my own, python
being my preferred language.

Lindsay Haisley       | "The first casualty when
FMP Computer Services |         war comes is truth."
512-259-1190          |            
http://www.fmp.com    |     -- Hiram W Johnson

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