I am using using Thunderbird 24.5 on a Slackware 13.37 system. I have an IMAP account A against a Dovecot IMAP server. I have access to A from this Thunderbird client, and also from a client in my Android phone. Things seem to work fine, but I have noticed the following: When I get an email in A, the email appears immediately (or nearly so, I guess) both in Thunderbird and in the Android client. If I delete this email in Thunderbird, it does get deleted in the Android client as well, at worst again after a short interval (seconds, it would seem).) Now if I delete the email in the Android client, it never gets automatically deleted in Thunderbird. When attempting to delete an email, the Android client gives me the choice to delete it locally or in the server. Either way, the email does not get deleted in Thunderbird. Any idea as to what is going on, and how to solve it? When I created the IMAP account in Thunderbird I did not change any settings to do with synchronization. My settings are the same as in https://support.mozilla.org/en-US/kb/imap-synchronization.