I have been using GPG for a long time, but I never got around to setting it up in Apple Mail. There was always something more important. But recently, I finally did it. The main problem was that I couldn’t find a suitable solution for iOS. I haven’t solved this issue yet, but if I need to work with constantly encrypted content, I would rather use ProtonMail or Tutanota.

So, PGP allows you to sign and encrypt a message. The signature ensures that the message has not been altered after it was signed by the sender. Encryption ensures that the message will not be read by third parties. Signature and encryption can be used together or separately. I always enable the signature, and encryption only when necessary.