I am trying to email a customer who's email address resides on secureserver.net. Each time I send them an email it bounces back with the following information:
550 5.7.1 SPF unauthorized mail is prohibited. (in reply to DATA command)
Remote-MTA: dns; smtp.secureserver.net
Diagnostic-Code: smtp; 550 5.7.1 SPF unauthorized mail is prohibited.
How do I fix this?