I have this too, thunderbird 45.5.1 on windows 10. When I move mails between folders, Antimalware Service Executable jumps to 25% (4 core cpu, so single thread 100% load).

Temporarily turning of malware protection in windows settings fixes it.

Dont think I experienced this on earlier versions of thunderbird.

I am using thunderbird 45.5.1 on Win8. I Am using AVG antivirus, but no specific Malware application. I ran the performance monitor and there was no increase in CPU usage, and the drag & drop did not work. I used the [Move to:] function and the emails were moved, also with no increase in CPU usage. Please do not suggest that I downgrade to W10!

Hell no. Thunderbird shouldnt work any different no matter what version of windows you use (Keyword "shouldnt").

If you want to try changing anything it would be to downgrade thunderbird to v44 or lower to see if the problem remains.

Personally Im just going to endure it and hope it gets fixed.

Does Mozilla monitor these fora? Perhaps they will see the issue and fix this unintended feature.

I have no idea. I have a feeling devs only browse here occasionally. Most devs dont go looking for bug reports in places like this. They want their bug reports neatly served to them on a platter (bug tracker, etc).

Ok folks, I have sorted out the problem with drag n drop of emails to folders in Thunderbird. I checked using Task manager and found that my CPU was running at 99% almost all of the time, with no other activity happening. I closed down all applications then re-started the computer. Hay presto, with Firefox and Thunderbird running all is well and the CPU is running at 20 - 30%.

I checked and now find that I can drag & drop multiple email from my inbox to any local folder in Thunderbird.

I hope this helps, Tony

TonyFromWestOz said

Ok folks, I have sorted out the problem with drag n drop of emails to folders in Thunderbird. I checked using Task manager and found that my CPU was running at 99% almost all of the time, with no other activity happening. I closed down all applications then re-started the computer. Hay presto, with Firefox and Thunderbird running all is well and the CPU is running at 20 - 30%. I checked and now find that I can drag & drop multiple email from my inbox to any local folder in Thunderbird. I hope this helps, Tony

That's pretty odd. Thanks for the update

Joonicks said

I have no idea. I have a feeling devs only browse here occasionally. Most devs dont go looking for bug reports in places like this. They want their bug reports neatly served to them on a platter (bug tracker, etc).

Volunteers monitor the support forums. (And we can always use more - hint, hint)