I need to clarify the problem. If this is an IMAP account, TB should be re-syncing upon start up. Are you saying that there are bodies of emails that are lost when you shut down? What exactly do you understand is happening that the 're-syncing' means it takes a long time?

Thx Frisee

Yes, it is an imap account, and yes, it should sync.

It used to 'cache' all the messages locally, then just check for and retrieve new ones. Now it seems to re-download everything, even things that should be cached.

Long time means days. Literally. And yes, I do need the messages locally, offline.

This will have to wait for someone more experienced. However, I'd be interested to know what TB is doing.

1. Keep TB open

2. Do you know where your profiles are? In Windows, they would be at: C:\Users\[User]\AppData\Roaming\Thunderbird\Profiles\XXXX.default-release then go to Mail and find/open the account you use Find the name of the folder in which the emails are. There will be 2 folders, one with the extension .msf. IGNORE this one. Write down the file size of the other. This contains all the data of your emails. Keep this window open.

3. Close TB and relaunch it.

4. Has the file size under 2 changed?

The reason I'm asking you to do this is for my own information - this happens to a few users. If TB is removing all the bodies from your emails then that file should reduce in size to almost zero after closing and re-opening as it removed data. If it stays the same (and yet TB starts to sync all over again) then that would be a different problem.

I have no idea how to solve either but it would be good to know just what TB is doing.

Thx Frisee

I went to the ImapMail folder (the Mail folder has some files but all have a size of zero K)

There are many folders in there, including many for the same account - some have old date stamps, and one or 2 are large (over 40 gigs).

See pic attached of some of the folders (there are other multiple folders for other mail accounts)

I wonder if these are old and can be deleted?

I closed TB and restarted, and the file size had changed, but very marginally.

It doesn't look like you got to the files I was asking about. You need to access the folder that is your current IMAP account that contains the data for the folder that you're having trouble with - then proceed. As there are five IMAP folders, I need to ask you whether you have five separate gmail IMAP accounts?

I have one Gmail account. The IMAP folder for that is imap.gmail-4.com. The others in the pic are for the same account, but seem to be old.

So, have you found the file and does as I asked so that we can determine whether TB is deleting data or simply not finding it?

If you intend trying to do something to the other gmail folders, then shut TB down first. Then drag the folders that you think are obsolete to somewhere safe. Keeping the window open, relaunch TB and see how it operates. See if TB has repopulated the open window with any other folders.

And keep the removed files for a week or so until you are absolutely sure there is no negative impact on the program.