Hah I had an interesting experience. I was trying to get Mutt to list the IMAP subscribed folders when there's nested folders but the behaviour was somehow inconsistent with what I expected/really odd.
Initially I thought this was due to a feature in IMAP that Fastmail didn't support (well they use Cyrus IMAP so the problem would stem from there). A back and forth with their customer service and they immediately piped it to one of their developers because it was technical and was discussing low level IMAP commands with debug transcripts from Mutt.
Turns out Mutt was using an outdated/legacy IMAP command that had been superseded by a new command with its own RFC.
Was able to patch Mutt and everything started to work correctly and look consistent.
It's not everyday you have a email provider service help you debug/troubleshoot your mail user agent which leads to actual improvements.
Initially I thought this was due to a feature in IMAP that Fastmail didn't support (well they use Cyrus IMAP so the problem would stem from there). A back and forth with their customer service and they immediately piped it to one of their developers because it was technical and was discussing low level IMAP commands with debug transcripts from Mutt.
Turns out Mutt was using an outdated/legacy IMAP command that had been superseded by a new command with its own RFC.
Was able to patch Mutt and everything started to work correctly and look consistent.
It's not everyday you have a email provider service help you debug/troubleshoot your mail user agent which leads to actual improvements.