IT Pro: How to avoid re-routing all company outgoing emails when using server-side

How to avoid re-routing all company emails when using server-side:

In the transport rule for Exchange online, you tell it to route only the messages where the body contains {EMAILSIGNATURE}.

Requirement: You must pre-define a text string or marker you want to use for telling Xink server-side to route and apply signatures those specific message.

Pros: No re-routing of email sent from Windows, Mac and Web, Outlook app for mobile.

Cons: The marker must be used. Large companies can set the marker centrally on all their mobile devices (MDM system).