I've mostly finished switching the list's SMTP server from notqmail (a qmail fork) to Haraka. Kind of a funny juxtaposition. Qmail is a C program whose design was already traditionalist when it was written in 1995, and it hasn't changed much since then. These days it's used mostly by hipsters. ;) Haraka, on the other hand, is written in node.js! As much as I like qmail, I wanted to take advantage of Haraka's flexible plugin system to implement the functionality I want: custom From address munging applied on a per-recipient level, only after an initial un-munged delivery attempt fails. I haven't actually finished that yet, but it's close.
I first set up Haraka last weekend, reimplemented the subscribers-only filter, and trialed it by having Mailman use it to deliver only list messages I wrote myself. (That way I could test deliverability to everyone without spamming them with test messages, while minimizing disruption if it didn't work.) This weekend, I didn't have enough energy to do much, but since logs didn't show any delivery failures for the handful of messages I've sent since then, I thought I might as well finish switching to Haraka. It's now handling all deliveries as well as incoming mail. Please let me know if there are any issues.