Mail app

Mail app keeps deleting and redownloading messages

Very interesting. I have a similar problem, but only since upgrading to Monterey. I completely deleted and re-added all email accounts, with no change in behavior. Mail opens, shows me all my messages, but then says “Downloading 1 of 345,000 messages…etc.” It seems to be mostly related to Exchange accounts that are part of an on-premises system (i.e. not Office 365) that we use at work. I can’t easily confirm if it does this for my GMAIL account as well.

I got to a point where I thought it had stopped working – I couldn’t see the messages downloading indication anymore and the network monitor (Little Snitch) seemed silent. (Previously it showed steady download network traffic for Mail on these Exchange domains.) But Mail has started doing it again. The only thing I could think MIGHT be involved is that I sometimes use a VPN – (Windscribe, to be precise), and after using that VPN, the whole Mail download process started again.

There aren’t enough logging/diagnostic tools to help understand WHY Mail is doing this, but it’s deeply annoying – especially since for the next few weeks I’m on a limited bandwidth internet connection and that I have already consumed most of the allowance for a month before the 10th of the month…

If you (or anyone else reading this thread) can help identify WHY Mail is doing this, and specifically what needs to be done to stop it, that would be VERY helpful!

I confirm that I have:
– Improved mail from Big Sur (original situation); this triggered the undesired download behavior again on Monterey;
– Rebuilt mailboxes (from Mail), which are supposed to effectively “start over” with message redownloading;
– had problems with search finding nothing more recent than about a month;
– removed envelope files from Mail, forcing it to “upgrade” things the next time it starts;
– apparently solved the search problem, since Spotlight and mail search now show me all relevant messages;
– completely removed and re-added all mail accounts (including effectively removing folders from /Users/…/Library/Mail);
– seen Mail STOP doing this for a few days (confirmed that Little Snitch no longer shows constant traffic);
– had this reboot, maybe after using Windscribe VPN;

All ideas/thoughts are welcome!!!