Recently, Thunderbird started to exhibit the following behavior: Copying a file to the Sent folder after sending a message takes about 10 minutes. Here are Thunderbird's IMAP logs: https://www.dropbox.com/scl/fi/wyvy2v2rlv111zzze7ggy/tb.imap.log-1.moz_log?rlkey=g02i0kloitely6qc4j3hca2zl&dl=1 We sent a test message around 2024-03-18 08:26:00, immediately after starting the logging. We finally see the message sent to the Sent folder on 2024-03-18 08:33:19.130595 UTC. I'm unsure when the message was finally written to the server. After this, there is also a problem opening the Sent folder. Basically, the new message won't become visible until after about 20 minutes. After initially waiting for this, the error changes a bit: Sending starts working, but updating the Sent folder still takes around 20 minutes. In other words, the sent message won't become visible after 20 minutes. After sending a message, it takes around 20 minutes to appear in the Sent folder.