I installed 3.1.0-beta and tested all use cases, everything is working properly now.

Great.
I'll wait for v3.1.0 then.

Hi aheinecke,
I did some tests with 2.0.7-beta10 and still found some issues.
The message I attached as a test case in previous comment is now properly handled, I see no "signature.asc" attachment and message is correctly tagged as trusted sender; this test message was sent from Evolution and I sent it to myself (sorry for not pointing this out before).

I just tested version 2.0.7-beta8 x64 and I can confirm the bug is fixed, GpgOL can decrypt messages properly. Messages also appear to be properly signed.

You can find the message attached.
Message has been saved from Outlook 2013.