The thing about offlineimap and isync (which I prefer because it is significantly faster in my experience) is they work great until they don't. I originally switched from offlineimap to isync, because of some bug (might have been offlineimap or exchange IMAP support, I don't recall) which caused some email loss.
Just this week I had to deal with some isync issue which causes the sync to duplicate mails when uploading to the server. I still haven't figured out what's going on, I'm getting Keywords not supported errors from the server when syncing, which caused this. It happened once before and I had to wipe the whole directory and resync to fix it.
I am now looking at what other solution to use. I used to use muttator which was a plugin for thunderbird that emulated mutt behavior and was great, but that hasn't been maintained for >7 years
I am now looking at what other solution to use. I used to use muttator which was a plugin for thunderbird that emulated mutt behavior and was great, but that hasn't been maintained for >7 years