How do I know if an email cannot be unencrypted in Outlook?

Question

When you use the Outlook API to access the Body of an email that's encrypted that you don't have the key for, Outlook throws an exception that says something like "Your Digital ID cannot be found by the underlying security system." Is there a way to determine whether an encrypted message (MessageClass "IPM.Note.SMIME") can be read without catching an exception?