I use two monitors at work. Thunderbird is always open on second monitor (Samsung A19B150) so I can monitor incoming mail whilst working on main monitor. From fairly recently, Thunderbird extends beyond the screen horizontally when maximised. This is very frustrating as it renders the scroll bars inaccessible This seems to relate to certain mailboxes. For some, including gmail and AOL, when I select the mailbox in folders pane the scroll bar appears, disappears then appears again. For others, including my two main work inboxes, the scroll bar is just visible off the right side of the screen, but inaccessible to cursor. The same thing happens with outboxes, but not necessarily in the same was as the corresponding inboxes. It isn't only the incoming mail list pane - the whole desktop width changes with different mailboxes. I tried changing scaling in advanced settings, but it didn't help and made emails harder to read as font size dropped. No other program behaves like this and Thunderbird seems to behave normally if I move it onto my main monitor (Samsung E2220). I don't want it there though, as it will be hidden behind the windows I am working on.