Hi there. I posted this question a few days ago but have received no response and now cannot find the original posting. :-( I could really do with some advice about an annoying thing that happens with TB. I have experienced this problem for some time but have recently upgraded my Windows 10 PC which ran version 102.14.0 (64 bit) to a new Windows 10 PC and installed version 115.1.0 (64 bit). Unfortunately, the problem still exists and if anything is worse. I have successfully imported about 15 years worth of historic data. What seems to happen is this. I go on line and successfully download my messages but if I then try to reply to a message when the connection is still open, I get the attached error message. I can click either “Retry”, which seems to have no effect or “Save”, sometimes twice which sometimes (but not always) files the message in my “Sent – phil@***********”” Local Folder, not the “Sent” folder as required.. Sometimes, the message disappears completely, which is most inconvenient. If I close TB (and obviously the connection) and reopen it a short time later, I can answer the message in question, send it to the Outbox by clicking the “Send later” button” and then upload it by clicking on the “Send Unsent Messages” option without receiving the error message or it being posted to the wrong folder. I have also tried moving / copying the “Sent – phil@***********”” folder to / with the “Sent” folder, but this does not seem to be possible. I have also tried unchecking the <Account Settings > Copies and Folders > Place a copy in> as suggested in an on-line Mozilla Support article https://support.mozilla.org/en-US/questions/1365695 but the outgoing mail completely disappears, being neither saved in the “Sent” nor the “Sent – phil@***********”” folder Is there a solution to this problem please? Regards and TIA