Need to change Guest User (Primary)

Good Morning,

We are having an issue with Service Desk Email monitoring.  Recently we enabled our Email notification service in Service Desk and now we are getting a lot of EM-###### stating that our email security appliance is detecting that our current GUEST USER EMAIL which is GUEST@SYMANTEC.COM is not recognizable.  So my question is how do I change this account to a Company email account.  We are using Service Desk 7.1.

ANy solutions would be greatly appreciated.

Jason John