User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322) Build Identifier: I'm using IMAP, all folders are marked for offline use and downloaded locally. The largest folder has about 6000 emails (1GB). I have set "When I delete a message - Mark it as deleted". After marking some messages for deletion in the large folder, and making sure that all the messages should really be deleted, I use the "Compact This Folder" command, or the "Compact All Folders" command, to really delete them from the IMAP server. The "Compact" commands perform an IMAP purge, but they also compact the offline storage files, causing severe performance issues. What's even more annoying, is that some of the operations are performed in background, and you have no visual cue that Thunderbird is the application that is slowing the system down. And if you close the application, it doesn't really close, but it continues to compact the files in background. So, there should be two commands available only for IMAP folders called "Expunge(Purge) this folder" and "Expunge(Purge) all folders". This commands should: 1. Execute IMAP purge on the server. 2. If the folder has offline storage, change the "mark deleted" flag in the offline storage to a custom flag "really deleted" that will cause the interface to completely ignore it. This will be much faster than compacting the offline storage. I know you won't like this: "Works fine in Outlook Express (TM)" :) Reproducible: Always Steps to Reproduce: 1. Create a large IMAP folder (more than 100 MB, more than 1000 mails) 2. Set "When I delete a message - Mark it as deleted" 3. Mark the folder for offline use, and download the folder locally 4. Delete some messages from the folder (10-20 mails) 5. Run the "Compact This Folder" command Actual Results: The mails are deleted from IMAP server, then Thunderbird starts compacting the offline store in background, slowing everything down. Expected Results: Should have provided an option called "Purge/Expunge" that will delete the mails from the IMAP server, then mark the mails as "really deleted" in the offline storage file. This will be much faster than compacting.

I'm not sure if I'd go that way, or figure out some other time/way to compact the offline store.

There should be a button "Expunge" beside the "Delete" button and it should Expunge in the current folder. So far I am using "mark as deleted" when I delete an email and the only way to really delete an email is to use the function "Cleanup Inbo on exit" which by the way cause two problems: 1. Not possible to cleanup any other folder than Inbox and 2. Once thunderbird is closed there is no second chance, the email is gone. So far Thunderbird is the first imap client I have seen without this functionality .

emre, see also bug 236922 move to core:imap?

would this even be absolutely needed if bug 218075 were fixed?