If you ask me for a contact email I will tell you something like [email protected]. Editing the FROM field allows me to write an email to you.

If you ever start sending me spam I can just block that address. Especially helpful with companies.

You can also use it for sorting emails.

It's honestly a basic feature of an email client. Even if you don't have your own domain stuff like the plus sign for aliases exists with many providers (or at least with gmail).

My usecase: I have one email account with multiple aliases.

I added it to iOS mail with the main alias. I registered to my bank using a secondary address, a more "neutral toned", also one I'd expect to be sold to data brokers, and would be willing to abandon easily if started to get too much spam...

Now the banking app is pretty... ripe for improvement.

I report a bug in the app, and the way it happens: it throws up an email editor, with debug info attached to a partially pre-filled form mail. However if its sender is not the alias I set up at the bank, it will get rejected, and will have to do lots if identification turns etc...

Apple mail does not let you set up aliases for an account, I'd need to log in twice to the same account to be able to do this. Also apple mail is a piece of ... modern outlook, to be really rude, so I'm interested in alternatives.

The official explanation is as follows:

    If your e-mail provider supports it, Customize From Address allows you to make a one-off minor alteration to your From address without having to create a new identity in Account Settings. For example, if your From address is John Doe <[email protected]> you may want to change it to John Doe <[email protected]> or John <[email protected]>.

Use whatever identity you want. A server that you don't personally own will not normally allow that however. One more reason to self-host email.