We use NetIQ to monitor Exchange 5.5. NetIQ had a script for oldest message in MTA. You can set a time period for the mail message that is stuck in the MTA, and when the threshold is reached an alarm is raised and we are paged.

I don't see this same feature out of the box with MOM and the Application Management Pack. Would we have to write a custom rule to do this? As I see it now, there are just some thresholds like >500 messages in a queue. With mass mailings we might hit these many times, and get false pages. Maybe there are Exchange MOM rules that already do this, but I haven't seen it yet, and just wondering if anyone else has run into this.

Contributed By: Chris Harris [MSFT]
Unfortunately, there is not a rule in MOM based on the oldest message in the queue.

The way the queue length rules are designed your queue should have to exceed the threshold not just once, but a number of successive times before an alert will be generated.