Thanks for testing, I posted in general thinking I could get random input from some subset of users that do use Thunderbird (because I doubt this issue has to do with M1 Mac specifically). Does anyone else happen to use NoMachine and Thunderbird and have similar issues dragging e-mails from one folder to another?

I also noticed a folder’s text continue to appear highlighted when I wasn’t pointing at it in one case, and I had to close and re-open in order to get that display artifact (presumably) to clear. When e-mails fail to move on NoMachine, the text appears highlighted, but trying to make sure the pointer is on the text doesn’t seem to make a difference, either. When e-mails failed to move on Windows or on the Mac Mini using VNC, it was clearly because the pointer was not touching the text of the folder, and you could tell because the text wouldn’t be highlighted (so it was arguably user error / poor Thunderbird UX). Prior to that, I was running Thunderbird on a Windows (7, Ultimate) PC and connecting from the same client using the MS Remote Desktop client and not having this problem (again, e-mails would seldom fail to move). Prior to my current scenario, I was connecting with ’s viewer application (6.21.406 (r44671)) and not having this problem when connected to the same M1 Mac Mini (e-mails would seldom fail to move). When trying to drag e-mails to different folders in Thunderbird, they often (almost consistently) fail to move. I’m currently using the NoMachine player (7.6.2, “Show remote cursor pointer” & “Grab the keyboard input” selected) on a Windows (10, 2016 LTSB) PC to connect to an M1 Mac Mini (Big Sur, 11.5.2) with NoMachine server (7.6.2) that is running Thunderbird (78.14.0).

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