McAfee has recently published the KnowledgeBase articles below to assist with McAfee Email Gateway and Secure Mail top issues:
KB71781 - SecureMail/Email Gateway: How to enable PGP encryption and decryption
https://kc.mcafee.com/corporate/index?page=content&id=KB71781
KB71788 - Secure Mail/Email Gateway: How to route mail for the domains hosted by the appliance
https://kc.mcafee.com/corporate/index?page=content&id=KB71788
KB71790 - Email Gateway: Why do messages go to the Failures quarantine?
https://kc.mcafee.com/corporate/index?page=content&id=KB71790