[BALUG-Test] Mailman3 testing

[Michael Paoli]

Have some very preliminary Mailman version 3 testing started on
the BALUG VM, notably for lists.balug.org
General plan (at least shorter term) is to replace the existing
soon to be unsupported Mailman 2 with Mailman 3.

So, testing on Mailman3 - presently have one list set up:
balug-test3@lists.balug.org
Note that it might possibly wink in and out of existence,
and/or get reloaded, etc., but general intent is for it
to mostly persist and have continuity through testing,
And around/after completion of Mailman 2 to Mailman 3
migration, will probably fold it into existing
balug-test@lists.balug.org list (which will then be Mailman 3).

At the moment, so far (probably) just email interface,
with other bits to come.

So, subscribe, unsubscribe, etc.
balug-test3-subscribe@lists.balug.org
balug-test3-unsubscribe@lists.balug.org
balug-test3-request@lists.balug.org

Note due to some limitations in how the MTA is
configured with anti-spam, it will generally
filter/reject/drop messages with empty bodies (presumed to be spam),
so, to work around that, don't have an empty body.
E.g. -request address, to send a command of help,
put it in the body, or if in the subject, include a body of:
end
so it makes it past the anti-spam and gets properly processed.
The existing Mailman 2 configuration has these MTA anti-spam configuration
limitations noted on the relevant web pages, and the relevant help text, etc.
... but I haven't yet done any such customization on Mailman3.