Dang. I set it up before but now it is unavailable for my account! Everytime I turn around there has been a security “enhancement.” OK I shouldn’t complain, but, in addition they keep changing the interface on the back end so when I search for answers, all the answers are old and the solutions have changed!
OK. I tried to add an alias to my gsuite gmail account and I got the dreaded:
“You must send through new-domain.org SMTP servers when you send as email@example.com. However, this functionality is not available for your account. Please contact your domain administrator for more information.”
All the answers were old enough so that the solutions had been moved and it took 4 or 5 differently phrased searches to find the correct answer.
Well, as of October 7, 2019 @ 1506 UTC here is the solution.
Log in to the G-Suite Administrative backend (if you don’t know how to do this then you obviously are not the account administrator).
Follow the menus to: Apps–>G Suite–>Settings for Gmail–>End User Access.
On that page you should find a setting for “Allow per-user outbound gateways.” Turn it on and then wait a day or so. Everyone in your organization should be able to add aliases going forward.