Forum Discussion
Transport rule for encrypted messages
Modifying the content on an encrypted message is not supported, as detailed for example here: https://docs.microsoft.com/en-us/previous-versions/office/exchange-server-2010/bb124703(v=exchg.141)#message-types
We currently have a rule that is prepending "EXT:" to the subject line of all messages from outside the organisation via an Exchange Online transport rule. This is also occurring on encrypted messages (coming from an external recipient also in Exchange Online). Is there any way I can create a condition to detect these encrypted messages and use this as an exclusion for this transport rule? I've tried using "if message type is encrypted" and if "X-MS-Exchange-CrossTenant-TransportEncryption-OmeV2LinkUrl' header contains "."" but with no success.
Even better I could create a separate rule to tag these messages with "Encrypted:" and bypass the above rule.
Depends on the type of encryption, how exactly are the messages being generated? RMS? OME? S/MIME?