Quoting Brian E. Lavender (brian@brie.com):
Mailman 3 seems to have taken more effort than Mailman 2.
Well done. I'm not surprised to hear that it was a bit of a bear.
I still need to configure reverse dns on the server and probably do some dmarc or dkim configuration.
You definitely need rDNS. Many SMTP sites de-facto penalise sending hosts that lack rDNS -- and some even penalise ones with generic-seeming rDNS -- despite that not being an RFC mandate.
You're probably aware of this, but there are RFC mandates for:
o must accept mail to abuse@ o must accept mail to postmaster@ o must accept mail from the null sender
On DKIM/DMARC, you might already be aware of my view of those standards from the Firm Formerly Known as Yahoo:
:r! dig -t txt _dmarc.linuxmafia.com +short "DMARC: tragically misdesigned since 2012. Check our SPF RR, instead."