SPF stands for Sender Policy Framework.
It's an email authentication system that verifies that a message came from an authorized mail server. SPF is designed to detect messages from spammers and phishers who falsify the sender's IP address in the email header.
VerticalResponse uses the SPF system, as well as DomainKeys, DKIM, and other systems to authenticate each and every email we send. This ensures that you'll have the best delivery rates possible.
With SPF and Sender-ID, we have published records that state our mail domains are allowed to send email on behalf of our own IP Addresses. With DomainKeys, we sign each email with a key that the recipient server can then use to verify that we actually sent the email. These are a very important part of maintaining a good sending infrastructure.