Email address in the From dropdown list using Apples Mail

I use a forwarding company to be able to use a "bikerider.com" email address instead of AT&T's "att.net" which is my real email address. Up to a few days ago, in Mail's Preferences there was a way to type this "fake" address into Preferences and get it as an option in the FROM box when sending an email. It may have something to do with Sierra, but I can no longer find how to do that. I've tried phoning Apple Help, AT&T Help, and Yahoo Help (that's what AT&T U-verse uses and it's impossible to phone Yahoo). Anyone have this problem and solved it?

Launch Mail, from the Mail menu choose Preferences. Click Accounts, highlight the account you want to work with, click the Email Address drop-down, then click Edit email addresses. You should be able to add the other address there.

It's important to understand, however, that using a mail server for "att.net" to send out an email for "@bikerider.com" would be considered SPAM by many of the various servers on the internet. So, you should actually set up the @bikerider.com address as an account to both receive and send messages.

Email From box

Great - it works! Thanks very much