If you have GSuite [email protected] is your gmail address. yourdomain.com's MX records will be pointed to Google.

This is different to the various techniques, such as IMAP/POP and forwarding, used to get [email protected] email (actually hosted elsewhere) into a [email protected] mailbox

I have it set up so that Gmail sends the mail through my domain's server. The <from> field is my domain address, and my gmail address does not appear anywhere in the header.

I've had it this way for a long time, but I believe it was optional and it's also possible to only read the mail from the domain but send it via gmail.

I'm not using GMail's web interface. My mailreader (Apple Mail) allows me to select from which address I'm mailing.

Admittedly this doesn't work from my mobile GMail app, but I don't send a lot of work-related email (which my alternate address is for) from my smartphone.

Admittedly I haven’t used gmail for years now but from what I remember when I used to do this this is half right. If you change the From address in gmail, it will add a ‘Sender:’ header with your gmail account on it. Some clients will show that combination as the email being from ‘X on behalf of Y’ where Y is the from address and X the sender address and some will send replies, especially bounces, to your sender address. It may also set off some spam traps. I think it might also have required some form of verification that you have access to the address in question.

If you want to send from a different address without the sender header being set to your gmail account, I think you have to have Gsuite.

I just looked at the headers from some emails I sent this way. My gmail address does not appear there and both the <From> and Return-path are my domain address.

Thanks. Looks like they fixed this quite a while ago and now either you can verify an account after which it will accept your From header (and the web and app UIs let you select that) or, if you haven’t verified the address then if you send an email through their SMTP servers it will rewrite the From as your gmail address and sets a new X-Google-Original-From header to the address you put in the email originally.

I just tested it and it does work from the Android Gmail app.

How? I just checked and couldn't find it.

You have to have added the other email addresses from your Gmail web page first, under Settings, Accounts and Import, Send Mail As. It will ask you for the server address and credentials etc.

Then when you compose a message from either the website or the Android app, your From address is a dropdown containing the addresses you set up.

https://support.google.com/mail/answer/22370?hl=en