[MM3-users] How to Increase outgoing mail volume for Mailman 3

Hello everyone,

We had a new client come on board that brought a list that had the largest out-going mail volume that I have ever dealt with. So I did what any sane server administrator would do that is running Mailman 3: I ran to Mark Sapiro for help! Here is what the Sage of all things Mailman counseled me to do:

1. Disabled VERP delivery. VERP can help improve mail delivery by delivering 1 message per SMTP transaction (I think I got that right). Using VERP is counter-productive as it can seriously delay outgoing mail delivery for a high-volume list. So you can use something like the following in the MTA section of your mailman.cfg:

[mta] verp_confirmations: no verp_personalized_deliveries: no verp_delivery_interval: 0

2. I configured Mailman 3 to run 4 outgoing runners. The default is 1. This action was the game changer. It allows Mailman to handle 4 incoming messages at a time instead of 1. My client's incoming list volume was high enough where it was overwhelming the single outgoing runner. Here is what I added to the mailman.cfg file:

[runner.out] instances: 4

Doing this step immediately solved the backlog in var/queue/out.

3. If you start up with a new server for a list that is high volume then keep an eye out for Proofpoint and Vade Security as they will block your new IP address quicker than Mark Sapiro can say "This is a bug. See <some Gitlab.com url>"

Mark, thank you!

-- Brian Carpenter Harmonylists.com Emwd.com