I would worry about using Postfix for a business. I've been running my own mail server for 25+ years using Postfix under the same domain, and once about 7-8 years ago incoming messages from GMail bounced because Google tightened its rules for server encryption. I added the DMARC or whatever else was required, and it all worked again, but to do this as a business, you have to regularly test sending e-mails from accounts with the big providers who make all the unwritten rules.

I set up a small law office with GMail for their domain, for this reason, and have a script ready to run a Postfix server if Google fails.