SPF Overview
Sender Policy Framework (SPF) is used to authenticate the sender of an email. With an SPF record in place, Internet Service Providers can verify that a mail server is authorized to send email for a specific domain. An SPF record is a DNS TXT record containing a list of the IP addresses that are allowed to send email on behalf of your domain.
To take advantage of SPF, you must publish an SPF record in the DNS. The record is a list of all the IP addresses that are allowed to send email on behalf of the domain. Adding an entry to your SPF record only makes sense if the sender can use your domain to specify your address in the correct way when they send email. When you configure a sending source to do this, they should also specify how to update your SPF record to accommodate.