And if you use IP address literals instead of paying for a domain, you get a free SPF: If the "From:"/"Reply-To:" fields contains only the email address with t

And if you use IP address literals instead of paying for a domain, you get a free SPF: If the "From:"/"Reply-To:" fields contains only the email address with the IP address literal, you get your "SPF" and it gets a much better score in order to avoid grey listing for the first transaction. And if there are no URLs in the content, even better. But that is common sense.