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.
