I have set Thunderbird Settings to delete messages from the server older than X. However, since switching to Windows 11 and setting up the client there, even though I have checked and set the boxes to leave messages on server and for at most 28 days (or 30), the messages are staying on the server for upwards of six months. In case it matters, my server is comcast.net pop3 995. Since I did not have this problem for more than fifteen years of using thunderbird, I am suspecting that there is a new bug somewhere.