Instructions for Mojave:
- Go to https://gpgtools.org/ and download the source code or checkout the mojave branch from [email protected]:GPGTools/GPGMail.git
- Open GPGMail/GPGMail.xcodeproj with XCode and do not convert
- File -> Project Preferences -> Shared Project Settings -> Build System, set to Legacy Build System
- Navigate to GPGMail/Classes/Logic/GPGMailBundle.m, hasActiveContractOrActiveTrial and add make it to always return true
- Build
- Restart Mail.app
- in Mail go to Mail -> Preferences -> General -> Manage Plug-Ins... and enable GPGMail.mailbundle
- Apply and restart...