While sending mail to a particular domain, every message sent is getting returned with the error: "550 5.7.1 SPF unauthorized email is prohibited."
A cause and solution is required.
The cause of this error message is not related to the Symantec Messaging Gateway. The receiving domain is performing a Sender Policy Framework (SPF) record lookup on your domain and that lookup is failing.
Contact the Administrator of the domain that is sending the bounce messages to determine why the lookup is failing in respect of SPF record checks against your domain. This will help determine where the misconfiguration of your SPF record is.