In testing different mail servers I find that Gmail will treat them differently based upon there hello line. I can't remember which one was accepted most but t

In testing different mail servers I find that Gmail will treat them differently based upon there hello line. I can't remember which one was accepted most but there is a difference. Also you need to look into if others on your netblock are sending spam. If you are on the same netblock as a spammer then gmail will treat you as if you are the spammer. This site is very useful if you have your own mail server https://www.senderscore.org/ https://www.senderscore.org/