I want to run a rule against a resource mailbox to move incoming messages to
a particular folder within this mailbox. When I attempt to run the rule it
does not pick up the existing applicable messages, however if I open the
resource mailbox via its profile, the rule fires automatically and the
message is moved to the appropriate folder.

Is there a better way to ensure that a rule fires other than having to open
the mailbox on a separate machine? As a delegate shouldn't the rule(s) fire
off anyway for any incoming messages to the delegated mailbox?