Warning MSExchangeTransport, Event 15002, on Exchange 2007

So last week Friday I noticed in the afternoon I hadn't received a single e-mail today. I open the Exchange Management console and don't see anything wrong at first glance. The event viewer contains however a few warnings: eventID 15002

I think: "OK, a warning, I'll look at that later ..." and open a command screen to telnet the SMTP port of our Exchange 2007 hub transport server. I immediately get the error: 452 4.3.1 Insufficient system resources back.

Hhhmmmm ... insufficient system resources ... resource pressure constantly high ... Hey, those things belong together ...

So I do some research on Technet and start reading into this a little bit. Appearently this is a feature, not a bug ... and it's called back pressure.

What can we do?
Well it's obvious that the best way to go is adding the resource you are short off. In my case: disk space. The limit is 4 GB and I had only 3,8 GB left on my partition.

Now, if you don't have that option, there is a page on Technet that specifies which keys can be changed in the EdgeTransport.exe.config file (XML based) that you can find under C:\Program Files\Microsoft\Exchange Server\Bin.
For every resource that monitored a key is present that can be adjusted. Of course, Microsoft does not recommend this and warns that adjusting the config file can lead to poor performance and data loss.

Still, I think this is a good new feature, but it should be more visible, not just a warning in the event viewer