Sender Policy Framework (SPF) is a simple email validation system designed to detect email spoofing. By defining a DNS TXT record for your domain, you can tell remote recipients which mail servers are authorised to send email using your domain.
For more information on SPF, visit http://www.open-spf.org/SPF_Record_Syntax/
Have you found a bug in the service? Please send us the link to the broken report and we will fix it as soon as possible.