Apple Core Rot extends to all areas of macOS. See Apple Core Rot: It’s Big Things, and Hundreds of Little Ones, that Together Add up to Chaos.
Here, Apple Mail hangs (at least an hour, and retry after retry). There was no problem at all with the mail server (on the local LAN, I run my own and I looked at the activity in real time and the logs)—purely a bug in Apple Mail.
I started and restarted it, turned off various accounts, etc. It finally just got past whatever bug it was running into.
It’s infuriating to just have Apple Mail decide to go haywire like this.
Charles C writes:
I've switched to Postbox. No more "recovered messages" folder (I had over a thousand---Apple never did explain what they were). I've had it about 3 weeks. Performing very nicely, with some great added features Apple mail doesn't have. Like a place to store canned responses to email that you can easily add.
MPG: worth looking into. A critical feature for me is POP support along with a "leave mail on server" feature, so that I can travel and do quick mail check on a laptop without having to lose the ability to then download it on my main Mac (update: a Postbox user sent me a screen shot showing that this feature is there, so I will need to look at Postbox).