Great tip from Jason Snell:

We get asked for our email addresses a lot, most commonly in login windows on websites. I’ve saved a lot of time by attaching mine to an auto-expanding text shortcut on both iOS and macOS. No additional software is required, though if you have a text-expanding utility like TextExpander you could use that instead.

I set this up with Nick Heer’s suggested shortcut of “@@” because of its placement on iOS’s email address keyboard.