Rebooting works as well, as does the usual shell updating. $ sudo defaults write /Library/Mail/Bundles/GPGMail.mailbundle/Contents/Info.plist SupportedPluginCo

Rebooting works as well, as does the usual shell updating. $ sudo defaults write /Library/Mail/Bundles/GPGMail.mailbundle/Contents/Info.plist SupportedPluginCompatibilityUUIDs -array-add "$(grep -A 1 "PluginCompatibilityUUID" /Applications/Mail.app/Contents/Info.plist | grep string | cut -f 2 -d ">" | cut -f 1 -d "<")" $ sudo chmod 644 /Library/Mail/Bundles/GPGMail.mailbundle/Contents/Info.plist The issue is that each version of Mail checks the available plugins for an explicit PluginCompatibilityUUID, which changes with each build. GPGTools 2 has updated its list on reboot (and install) since the beta stages, so if you're on a recent version, you should be good.