Sometime one email account has more than one email address or aliases.
After OsX, it has become more difficult to set those up in Mac Mail OSX or iOS.
If you’re using a standard IMAP, POP, or Exchange account, all you should need to do is find the field listed as Email Address, and add a comma followed by the other address.
Now, when you send an email, place the cursor over the From line and choose from the drop-down menu which address you’d like the email to come from.
On iOS, if you’re running a standard IMAP or POP account, you should be able to add additional email addresses with ease.
In the following screen tap on Account and then tap on Email: You’ll see a screen listing the primary email address and then an entry for Add Another Email.
Tap that and enter the email address you want to use, then hit the Return key on the keyboard (make sure you do that, because if you navigate away from the screen in any other way, it won’t save).
When you’ve done that, you should once again see the Add Another Email entry below your new address.
Now you can back all the way back out.
Make sure to hit the Done button in the top right corner of the previous screen.