I've run our email server for the last 7 years. Don't have any trouble with gmail. Setting up was a bit of hassle, but since it was up, I don't do anything wit

I've run our email server for the last 7 years. Don't have any trouble with gmail. Setting up was a bit of hassle, but since it was up, I don't do anything with it. Occasionally I will get the odd notification that a (usually German for some reason) email address doesn't like our domain. But the major providers, never had a problem. No idea why we haven't had a problem, I didn't know what I was doing at the time (still don't) just followed an online guide. From memory, spf, dkim which I think is all pretty basic things to setup when setting up a mail server and all guides cover it.