For example, something that is too complex for your comfort level, a security concern, or maybe your hardware can’t keep up with the service’s needs?
For example, something that is too complex for your comfort level, a security concern, or maybe your hardware can’t keep up with the service’s needs?
True, but this has nothing to do with Google and other, is a well done method to avoid spam.
so what else is a factor for reputation? Or is it like if you dont pay to get your mail-domain whitelisted we lower your reputation score?
No idea! I don’t run my own mail server. But if you read a bit up here, there’s a guy who runs his own mail server(s) since years. But the selfhosted world seems to be full (well…not so full) of people that self host their mail server.