Earlier quoted context omitted.
You can actually set up gmail to send through an external server? I had no idea they’d support that. Running an SMTP server is absolutely not something I’m willing to do, though. Aside from the general setup/maintenance hassle, all the big companies are aggressive at blocking spam and private SMTP servers are just tough to keep unblocked these days (or so I read).
If you have GSuite you can, but I doubt it is possible for individual accounts. [1,2] You can however send email to google's SMTP server, using an ordinary gmail account [3]. This is how email clients (Eudora, Apple Mail, sendmail) work. The only trick is that they force it to be authenticated and encrypted. I believe (but have not verified recently) that if you send an email with an email address/domain other than o…
Sending from Google's servers using my address would cause SPF and DMARC failures, so if you want to do that then they'd have to make sure it's clear that the mail is actually from gmail.