[dw64]

Having hosted a small mail server for friends for over a decade now, I can only think of this as a myth.

Gmail has specific bulk (!) sender requirements, which to my knowledge don’t include a blanket downranking of residential and „VPS“ IPs (the latter are just datacenter IPs anyways). You need TLS, SPF, DKIM, DNS and reverse DNS entries that align, ideally DMARC and that’s pretty much it.

https://support.google.com/a/answer/81126?hl=en#zippy=%2Creq...

At one point I misconfigured a relay as unauthenticated and we got abused by spammers for a day. We got put on all sorts of blacklists within hours and got our IPs cleared self-service immediately after fixing the issue.

If you just send emails completely unauthenticated, yes they will be blocked.