This is a regression, it does not occur with VSD 3.3.2 (gpgol 2.6.0).

While testing around T7722: GpgOL: Temp filename creation fails to choose proper extension I noticed that starting outlook and not selecting any mail caused the CPU load to be high (at least >30%) for as long as I did not select any mail. Or deactivate GpgOL.
In the process explorer appear repeated new gpgme-w32spawn.exe and gpg.exe processes.

Necessary to trigger this was a certain OpenPGP signed test mail with a very long subject (> 256 characters) at the "top" of the mail folder. Selecting it stopped the spawning and the load.
Deleting it stopped issues with the inbox folder, the same issue now occurred when switching to the "Deleted folder".

Gpgol.log (+call tracing) is in the shared folder, Markus.

If I had clicked on the mail with the very long subject, GpgOL asks on closing if changes to the message should be saved. No idea what changes Outlook means, it have to be automatic ones, I did not change it.