I am reaching the limit of my IMAP folder. With the idea of moving some of the largest emails to a local folder, I used Thunderbird's search function, found around 300 Inbox messages over 5MB, dragged and dropped them into a dedicated local folder using a second window (the "Move to" feature seemed to do nothing). These messages disappeared from my Inbox folder but surprisingly my IMAP storage use didn't budge. My guess is that moving the messages to the local folder does not actually delete them from the IMAP folder? The problem is that I cannot see them any more in the IMAP/Inbox folder in Thunderbird. I tried copying them back into the IMAP Inbox folder, hoping they would reappear, but it started actually physically copying the messages even though I presume they are already still there.

My questions are:

  • How can I move (large) emails from Thunderbird to a local folder and remove them from the corresponding IMAP folder, freeing up space on the IMAP?
  • Assuming I have moved emails from Thunderbird to a local folder but not removed them from the IMAP folder, how can I remove them from the IMAP folder?

1 Answer 1


There is a "compact folder" functionality for that. If that does not work even in offline mode Your profile may be corrupted.

  • Please correct me, but "compact folder" should affect the local representation of the mailbox folder only, not the cloud inbox? Struggling with the same problem in 2023...
    – Martin
    Feb 28, 2023 at 15:03
  • Sometimes it may take quite some time (several minutes) until moving/deleting mails translates in reduced quota usage. Nevertheless, even then I feel some discrepancy of the MB moved vs the MB that became free.
    – Martin
    Feb 28, 2023 at 15:11

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