I built an asp.net application that sends text messages to our employees using carrier-provided email to SMS gateways. The people on Cricket (sms.mycricket.com) are the only ones that are bouncing with a return message like this: Unknown address error SPF FAILURE/Sender has no SPF records: SEE RFC 4408 - FROM check failed: Received: from unknown (HELO servername.domainname.com) ([ipaddress]) by .... with ESMTP/TLS/DHE-RSA-AES256-SHA; 14 Nov 2012 06:22:56 -0600 From my research it looks like we may need to setup something in DNS for the Sender Policy Framework. I'm not in the networking group so I don't know much about this. How can this be done? http://en.wikipedia.org/wiki/Sender_Policy_Framework