4.2 with Outlook 365 continually tries to sync my inbox which causes it to be too slow to use. Uninstalling fixes the issue. It happens when an encrypted email from a trusted address comes in. It eventually works but can take hours to resolve whatever is going on.
Any ideas?
Probably, the best thing you can do is enable logging in GpgOL and see if you find something that tells us what the problem is. How to activate logging is described in the wiki.
Another question whose answer could help: Have you enabled S/MIME in GpgOL?