Trying everything, no luck with smtp working

It’s hard to guess what “everything” is means. Using the free Gmail for sending mail is against their terms of service. We’re you using regular Gmail? It’s pretty hard to get Google mark configured even if you are paying for it; there is a #howto for that, I believe, but I can’t find it quickly.

Have you tried a recommended smtp provider like mailgun? Have you tried Troubleshoot email on a new Discourse install?