Stephen Usher put forth on 3/5/2011 10:04 AM:
I know that this is a somewhat old thread but I do have some useful input.
Basically, this seems to be a Thunderbird problem (or at least an interaction problem between Thunderbird and Dovecot).
Before Thunderbird version 3 there wasn't a problem, the mailbox within Thunderbird would sync correctly. As of version 3 they seem to have changed their mailbox header list caching code and it gets horribly confused when mails disappear from the mailbox without it doing so. The only way to fix the view within the program is the rebuild the (Thunderbird) index.
This is not the only problem TB3 has with Dovecot. Quite often if there are large attachments TB doesn't fully load the attachments (and sometimes not even the mail itself). I've found changing TBs setting so that it only uses one connection to the server rather than the default 5 helps mitigate this.
I'm not sure why TB3 has such a hard time when talking to Dovecot as no other clients have any difficulty and TB2 never did.
I don't believe it's an issue of Tbird talking to Dovecot, and I don't believe it's a Dovecot issue. I believe it's a combination of the TB GLODA system and local folder synchronization. I recommend you disable both of these, close TB, then manually delete all local cached folder/message copies and the gloda database in the user profile, then launch TB. And never reenable local sync or GLODA. This should fix your problem. And make sure *all* IMAP clients accessing the mailbox expunge on exit, including your smart phone, etc.
-- Stan