This answer implies that you have no idea what the problem is, which doesn't bode well. The problem is that the major email hosts send to the spam folder any e

This answer implies that you have no idea what the problem is, which doesn't bode well. The problem is that the major email hosts send to the spam folder any emails from IP addresses they don't explicitly trust. My solution to this is just to ignore it and tell people if they want to receive my email they should work out how, as the problem is on their end not mine. But lots of your customers won't like that answer.