Using GpgOL from Gpg4win 3.0.0:
An S/MIME encrypted email that has been successfully send, cannot be opened in the send folder.
Originally this report was broader and about:
Several Users report, that they can't decrypt mails that are encrypted and signed via GpgOL, or that encrypted and signed files via GpgEX are corrupt.
This may also cause issue in T3441.
The Logs we received until now to analyze the issue further: