Rule to highlight mail when an accepted domain is used as the receipts address

HI,

I have a situation where there are multiple accepted domains but it's required that when mail is accepted to one that a rule highlights or appends something to the subject.

Essencially I need mail sent to the "old" domain to stand out. A rule that can be set at server side, globally, would be useful.

I'll be using Exchange 2013 but would like a test solution for 2007 also if possible. A group policy option might be useful?

Thanks

Chris