[tor-project] upcoming change in mailing lists configurations

[Antoine Beaupré]

Hi,

TL;DR: we are going to enable DMARC workarounds on Mailman mailing
lists, which should improve deliverability. You may need to change your
mailbox filters.

# What is happening?

We are going to change the configuration of all Mailman mailing lists to
set the `dmarc_moderation_action` to `Munge From`.

This will change the `From` header of outgoing email from mailing lists
(such as this one) from, say:

    From: "Antoine Beaupré" <anarcat at torproject.org>

.. to something like:

    From: Antoine Beaupre via tor-project <tor-project at lists.torproject.org>

# Why are we doing this?

This is because some email providers comply with the DMARC standard. To
give an example, say provider example.com says that only them is allowed
to send email from that domain and a user at example.com sends an email to
one of our mailing lists. It's possible that this email then ends up at
provider user at test.test, which, when it looks at the DMARC policy, decides
to refuse the email because example.com doesn't allow
lists.torproject.org to impersonate it.

The net effect of this is that user at test.test will not get the email (at
best) or (at worst!) get unsubscribed from the mailing list even though
their email provider is actually complying with the email standard.

A longer discussion of this happened in the issue tracker, here:

https://gitlab.torproject.org/tpo/tpa/team/-/issues/19914

# When?

This change will be performed in one week.

Tests have been going since August 24th on the tor-relays@ lists and it
has actually solved issues there, while not causing any other problems.

# How?

TPA will actually change the configuration on all lists, in the
backend. List admins wishing their list to be excluded can notify us by
replying to this email or opening a ticket in the TPA issue tracker, as
usual:

https://gitlab.torproject.org/tpo/tpa/team/-/issues/new

A.

-- 
Antoine Beaupré
torproject.org system administration
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