#Check txt record dig domain.tld txt SPF Record Testing Tools
http://www.kitterman.com/spf/validate.html
SPF Record Syntax
http://www.openspf.org/SPF_Record_Syntax
#Check Reverse DNS dig -x 123.123.123.123 Create a SPF record on TopHost
http://www.mail-tester.com/spf/tophost