I too would strongly advise you to use Google Workspace (the recent new name for G Suite, previously known as Google Apps). It's cheap, very reliable, and has all features you can dream of, including an autoresponder. It's unrealistic to think that it's possible to beat a service that costs a mere USD 6 / user / month (and is free for nonprofits!).
You're advocating
I'm not advocating, I give the OP an advice, which he is (and you are) free to ignore.
storing confidential business or personal data on the servers of the world's largest data mining company, and one that is rapidly becoming quite evil.
That's nonsense. I will give one example: Airbus, the European aerospace corporation, uses Google Workspace. If there is one single company in the world that would have every possible reason to not store their "confidential business data" on the servers of an American company, it's Airbus. Yet they do it.