iPhone I need to send from a domain email address within Gmail app on iOS

[wpshala]

I need to send from a domain email address within Gmail app on iOS, and also set this as the default address.

This is easy to set up on desktop. I'm using smtp.mailgun.org

Why do these settings for various domain email (mysite.com) addresses not just appear on iOS app once set up on desktop? Is this actually possible?

In the iOS app I have the option to add another account, select Other (IMAP), but it fails to connect to the server.

What is the best way to send from email@mysite.com on an iPhone?

 

[one more]

If you are talking about Gmail app for iOS, I can confirm that once you setup your custom address in Gmail on your computer (or iPad for that matter in a desktop site mode), you can send emails from that address when you create a new message and then choose it from a drop-down list in the “From” field. I have my professional email linked to my Gmail account in this way and it works flawlessly in iOS 12.

 

[wpshala]

Thanks, user error
It works fine