On the Mac when I’m sending emails encrypted I prefer to use Thunderbird email client from Mozilla. It’s an accomplished, fully featured email client with all the bells and whistles. Using the Enigmail plug-in makes it work with GPG Tools seamlessly.
To encrypt files on the Mac, I’ll use GPG Tools through the Services menu. This is whether I’m encrypting files just for myself or to send to somebody else. Obviously, I need the public key belonging to the other person.
I also have FlowCrypt set up in Gmail in the Chrome browser. Works with PGP keys and is really good.
If I don’t need to encrypt a file, but I want to have it protected while being sent through the system then I would use Firefox Send. It’s simple to use for the centre and also for the recipient.
I also have an application available called Encrypto. It’s easy to drag-and-drop a file into the application, give it a password and send to my recipient. I would send the password using a secure messaging service. You can also use the telephone to pass on the password. Or just give a hint to the recipient. Encrypto is just for Mac to Mac communications.