Sender Policy Framework – An authentication protocol used by recipient sites to verify that the originating IP address is authorized to send email for the domain name declared in the “MAIL FROM” line of the mail envelope. SPF is used to identify messages with forged “MAIL FROM” addresses.

3 Quick And Easy Ways To Build A Profitable Opt-In List
You finally realize that you need a good opt-in list. After reading countless articles and sought expert advices and have read many success stories of people creating a small fortune with opt-in lists you finally decide to have one of your own.