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!).
I would not advice any company that is continuously being fined for breaking the law.
This is not only an overstatement, it is completely irrelevant. Given the OP problem statement (small business, part-time admin, newbie to mail servers), I do not think there is a better solution. A small server already costs 20 USD / month, running a mail server consumes a significant amount of resources, and as the OP mentions running a mail server also represents a high security risk.