Some items are not correctly expunged

In Thunderbird, if you delete an item from any folder other than the Inbox, the item is marked as deleted but might not be expunged unless you move it to the Trash folder.

Thunderbird cannot connect if the IMAP endpoint is configured to allow unencrypted connections but also has an SSL certificate

To resolve this issue, you must change the IMAP endpoint to use SSL so that unencrypted connections are not permitted.

IMAP folder names

IMAP folder names must not exceed 256 characters.