Name Thunderbird Version 115.12.1 Build ID 20240618125055 IMAP account on HostGator. In the last 9 months or so, every once in a while (sometimes several times in a row!) when replying to a message, Thunderbird does not set the \Answered flag on the IMAP server. I enabled IMAP logging and finally caught this happening. The reply is sent and copied to the Sent folder, as it should, but the original email is never flagged as \Answered. I can't seem to see a pattern why Thunderbird skips this step, occasionally.