Yes you can. You have to jump through a couple of hoops to get there, but you can. Look for "Send Mail As" under "Accounts and Import". If you have to put in SMTP details, put in gmail's own SMTP server.

This is the exact same setup I have. Main downside is if I use a third-party email client like Outlook or iPhone’s built-in mail app, I can’t select the from address. Which means I have to use Gmail‘s horrible iOS app which doesn’t seem to work offline or cache anything locally. Still the best overall setup I’ve found, but far from perfect.

That sounds pretty much like spoofing to me and not as actually sending from that address. Or does Gmail also give you the option to add the necessary DKIM and SPF records to your domain?

‘Actually sending from an address’ is a concept that doesn’t exist.

If you want, you can limit the hosts that are allowed to send mail coming from your domain using SPF. Google does not control your domain so they can’t force, forbid or give your the option to do anything, but they do have a supported way for you to add their servers to the list.

This is all legacy though, if you set up a new alternative address you have to allow Gmail to send the messages through your own SMTP server.

I was just paraphrasing the concept of authentication for email domains. That's what DMARC is doing and why I mentioned DKIM and SPF.

I was unaware gmail free has a supported way to add the correct SPF records. Though thinking about it, even unsupported might be as simple as regularly scraping them from gmail and hosting them on your domains DNS records.

But they probably don't support DKIM through that (now legacy?) hack, which granted, isn't that important if emails come from a gmail mail server.

I think that's the point. People who don't trust Google don't want their emails going through Google's mail servers.

Sigh. I think we're drifting off topic. Back to my original comment, some DNS providers offer mail forwarding as a service for your domain.

It can forward to any email account/mailbox. e.g. Fastmail or ProtonMail or whoever.

I just happen to use to to forward to a gmail account. I think mentioning that was my mistake given the current sentiment as it distracted from the point I was trying to make.

@Sendotsh then pointed out what he thought was a limitation in using Gmail this way, which I responded to, and here we are. :-)