Issue:
A message was flagged to be a secure message (i.e. has "++" in the subject line) but is received by the recipient as a normal message instead of a "protected envelope". (Note: A message sent in a protected envelope is received by the recipient in a format requiring it to be opened using a special process-- see the page at the link at the bottom of this article for details on that process.)
Explanation:
Messages sent to external recipients: When Office 365 receives a message flagged to be processed as a secure message, it will first check our list of trusted partners for which email must be transmitted over a secure channel known as TLS. In those cases, the message will be sent normally but over the secure connection. This means the recipient will receive it like any other message. Because the message was transmitted over TLS, there was no need to further protect the message in a protected envelope, and you can rest assured that it was protected during transit.
For all other recipients, the message will be wrapped in the protected envelope and "[SECURE MESSAGE]" will be prepended on the subject line. This envelope protects the message while in transit over an insecure connection.
Messages sent to internal recipients: If you send a secure message from your UTHSCSA mailbox to another UTHSCSA recipient, will be received as a normal message. This is expected behavior as the "++" on the subject line only triggers the secure mail process if the message leaves UTHSCSA's mail system. Messages sent internally are delivered directly and securely from you to the recipient without ever leaving the UTHSCSA mail system, so the secure mail process is not triggered.
For more information, please see the following article:
https://uthscsa.teamdynamix.com/TDClient/2009/Portal/KB/ArticleDet?ID=92006