massive deletes (thousands of messages), usually result in data corruption, not harmony. The protocol is over 20 years old and was written when mailboxes were 5Mb and an email was a few kb of text.

Note also that Thunderbird does not live in the Google labels universe, so deleting mail that is in the inbox or other folder from all mail will see it reappear in all mail in the next synchronization.

A better approach is to use POP to download all mail from the gmail server and delete it as it goes (that messes up your pretty folders in gmail) do your housekeeping.

Add the same gmail account to Thunderbird as IMAP and drag the remaining mails back to the gmail account.

wow, that seems overly complex solution for dealing with just 5k messages.

anyway, jpapan, did you solve your issue?