I wanted to give everyone a quick update (reply-to set to just me, so send your gripes/complaints/whatnot there) The mail backlog is cleared. There were approximately 60k e-mails backlogged to go out to people which is now caught up. I learned about a script called qshape which can tell you what domains are backlogged. It was largely who you would expect. I cranked some options on postfix to allow more concurrent connections for mail delivery per message and have adjusted mailman to split into groups as well - these should hopefully be the right balance to keep mail flowing quickly. smtp_destination_concurrency_limit has been set much larger (500) which also helped clear the backlog faster. I’ll keep monitoring things to figure out what else needs to be adjusted. Apologies for not meeting expectations. I will refund you a full month service fee :-) - Jared