[Mailman-Users] smtp-failure.log / diagnosing delivery to only some subscribers

[Stephen J. Turnbull]

Christopher Adams writes:

 > So, I assumed that smtp-failure.log would show which addresses were not
 > sent to. I don't think that is what it is for.

No, it shows addresses that were sent to and rejected by the remote
SMTP server.  MTAs have another option, which is to accept and
silently discard the message.  In that case, neither Mailman nor the
local MTA will know that the message didn't arrive at the intended
destination.

Discards happen in several instances, of which I can remember three
offhand:

1.  Google famously discards posts returning to the same Gmail address
    that posted it, and automatically marks the original "read".  I
    suspect it does the same with duplicates where a mailing list
    subscriber is also an explicit recipient, but I've never
    experienced it or heard a complaint.

2.  Many MTAs will silently discard posts they've judged to be spam.

3.  Some users hit the "spam" button instead of "delete", and
    (depending on their mail client/ISP) that may mark your list as a
    spam source, autotrashing your posts in the future.

 > Any suggestions on how to troubleshoot why the message seems to be
 > only sent to a portion of the subscribers, though Mailman tells me
 > it was sent to all the subscribers?

1.  Gmail users who don't receive own post should be asked to look in
    their "Sent" folders.  This is a Gmail feature that Google thinks
    is a good idea, it is widely hated, there is nothing we can do
    about it -- have the user complain to Gmail if it really bothers
    them and eventually Google may do something to fix it.

2.  In general users who don't receive posts should be asked to look
    in their spam folders, and whitelist your list.  How that is done
    depends on the user's mail client.

3.  Do traffic analysis.  If all the users losing posts are at Gmail,
    or Yahoo, or at Hotmail, or at AOL, or some combination of the
    above, then one or more of the big services has decided you're a
    spammer, or that some topic or content that your list regularly
    carries is a spam signal (which results in intermittent failures
    for the affected users).

4.  Check the "blackhole" services to see if your site or IP is
    listed.

Much of the above and more should be somewhere in the FAQ.

HTH