[15457345234]

> thunderbird frequently reports that one mailbox is 'locked' because thunderbird crashed while accessing it several years ago

That's a lockfile left over on the local filesystem. That's caused by Thunderbird having two threads open on the same folder (i.e. you ran 'update all folders' and then 'compact folders' and they're overlapping)

If you open TB, let it sit for a while, then do file>offline>sync now - then let it complete - make sure all the folders are selected for local download (if this is applicable or viable for your use case)

then wait a while

then do 'compact folders'

it shouldn't happen again

You might also want to go into the 'account settings' and turn 'maximum number of server connections to cache' down to 2 - some IMAP servers get really bothered if you open too many connections to them. It's meant to autoadjust but it doesn't always. 2 lets you have one connection always open to the inbox for push mail and one available for working on other folders.

[NikkiA]

> then wait a while

Yeah, that was underselling it a little, it took over an hour to download all 60,000 emails.

Time will tell as to whether it happens again, but regardless, thanks for the pointers.

[15457345234]

Yeah TB behaves a lot nicer when you have a 100% complete snapshot of the IMAP account locally; a lot of things in it seem to work a lot faster and more predictably when all the folders are fully synced.

I'd run that 'offline->download/sync' every week or so. It'll automatically sync every folder you open, but running that syncs them all, and if you're an organisation fiend like me you have like 100 folders.

In addition you can take a manual backup of your email now by just zipping up the thunderbird profile folder. Always useful.