Encrypted Email Exceptions
Email exceptions reports may include information about encrypted emails which cannot be opened. Two common encrypted emails are Secure/Multipurpose Internet Mail Extensions (S/MIME) emails and restricted permission messages (RPMSG).
S/MIME emails include a digital signature added by the sender to verify his or her identity. The recipient has public key which is used to encrypt the message, and a private key which is used to decrypt the message. So S/MIMEs serve a dual purpose by both authenticating the author, and protecting the contents of the message. Microsoft Exchange supports S/MIME.
RPMSG messages are Outlook encrypted emails which may be set to prevent them from being printed, forwarded or copied by a recipient. A message with restricted permissions will have the extension 'rpmsg', and may appear as an attachment in another email. It will not be possible to open the message unless you are using the account of the recipient, and it may be necessary to use Outlook's specific rights management system. It may still be possible to review these messages by having the original custodian collect his or her email data.