add TXT SPF Record on your domain that includes your MX record IN TXT "v=spf1 a:mx1.theemailserversdomain.com a:mx2.theemailserversdomain.com a:mx3.theemailser

add TXT SPF Record on your domain that includes your MX record IN TXT "v=spf1 a:mx1.theemailserversdomain.com a:mx2.theemailserversdomain.com a:mx3.theemailserversdomain.com ~all" and then check out http://old.openspf.org/dns.html http://old.openspf.org/dns.html If you want on that site you can look on other domains examples.