I own two computers running MacOS 10.15.7 Catalina and have Thunderbird installed on both. Until rather recently, the Thunderbird version was 140.8.1. Then I noted that it was impossible to send e-mails, and soon discovered that the cause was outdated server settings. They could not handle office365, so I installed Thunderbird 148.01 and changed to settings that should be able to do so. This worked very well on one of the computers, the one which has a fast (SSD) hard drive, but not on the other that has a slow (non-SSD) drive. The error message that I get with the slow computer is, surprisingly, the same as I got with the older Thunderbird. But I suspect that the real cause is some kind of timed-out process. If any of you could explain what happens and tell me what to do, I would be very happy. Maybe I should choose a Thunderbird version somehere between 140 and 148? Helge Malmgren