[paulmd]

If google was running a smtp server for google customers use, and you figured out how to spoof like you were a google relay so they’d carry messages for clients who were not customers, and then you tried to open up a service reselling this capability as a commercial offering, you’d absolutely be banned.

That’s what discord and signal and apple and Reddit do too. It’s your service, you are under no obligation to provide it for free to third parties. And this is true even if you are a gatekeeper - google is under no obligation to provide guaranteed open smtp or even open transit into their network (they block a lot of domains etc), even if that is cumbersome for you personally.

Forcing that would be bad for everyone because gmail would immediately devolve into a pit of spam. As would iMessage.

It’s silly to pretend otherwise and would be openly acknowledged as such in any other context other than apple-bashing.