This app works great with other Mac users running GPG, but recently I've had to interact with someone using the commercial PGP v. 9.5.1 and Outlook, and it's not quite as smooth. I'm unsure if this is an issue with GPGMail or with GPG 1.4.5 itself, or more probably, Outlook/Windows.

I have GPG configured to not automatically decrypt, so when I click the decrypt button on an encrypted message, nothing happens, until I click to a different message, then back to the encrypted message. When I click back, the message is decrypted, albeit with quite a few "=20" linefeeds. Encrypted messages with attachments just don't work at all.

Just for fun I'm going to install GPG and Thunderbird on a Windows box and see how the interaction goes.