[Mailman-Users] cause of bounces

[Stephen J. Turnbull]

@mark:

The Hotmail error message does make it sufficiently clear that these
bounces are due to DMARC.  I will probably file an RFE to catch these
against Mailman 3.  Would you like me to do that for Mailman 2, or is
this "obvously not worth it" in your opinion?  (I intend to supply
code "eventually". ;-)

I should also fix the FAQ to mention the names of the new options, no?

@paul:

Mark Sapiro writes:

 > On October 9, 2017 11:56:02 PM PDT, paul at tokyoprogressive.org wrote:
 > >Hi and hope the answer(s) to my question are relatively simple. On one
 > >of two lists I manage, some people are getting deleted due to too many
 > >bounces.  And the bounces seem to be related to their mail provider not
 > >allowing the messages.   As far as I can tell, the main culprits are
 > >gmail, yahoo, and hotmail.

The messages that *cause* the problem are from Yahoo! and Hotmail
users (I just ban posting from those addresses, but I can do that
because using them for university business is against Monkeyshow =
Japanese government policy ;-).  Many large providers will bounce
these messages when resent via Mailman (and most featureful list
managers).

Gmail does "quarantine" these messages by putting them in "spam".  (I
think this is the appropriate action, both according to the DMARC
standard and according the the "finger in eye" theory of corporate
rivalry :-).

 > I think this is a DMARC issue. See
 > <https://wiki.list.org/x/17891458>.

The Hotmail errors explicitly state that "on behalf of" messages
violate Yahoo!'s policy, so yes, this is a DMARC issue in at least
some cases.

I suspect the reason that this "suddenly" came up after changing the
list's Reply-To policy is that some Hotmail and Yahoo! users started
sending to list when they hadn't been doing so before.

Note that the relevant option name has changed in recent Mailman; it
is now Privacy Options -> Sender Filters -> DMARC Moderation Action.
You almost certainly want that set to "Munge From", and the following
option DMARC Quarantine Moderation Action set to "Yes".  (Note that
"quarantine" is a setting on the mail sender's side; Mailman neither
knows nor cares about Gmail's quarantine policy.)

If subscribers complain that Yahoo! and Hotmail users' mail now comes
"From: LIST on behalf of USER (EMAIL) <LIST at YOURDOMAIN.TLD>" but
others come "From: USER <EMAIL>", you may also want to set the third
option DMARC None Moderation Action to "Yes".