I thought I'd contribute a MRTG configuration that graphs the number of messages received per minute by an IronPort appliance, specifically threat v. clean messages. This uses the API for AsyncOS 5 and can be modified to get at other information if you grok perl.
You'll have to edit the perl script to change the settings found near the top for your appliance. I highly recommend that you make a guest account on the appliance for the perl script to use.
I don't see a way to attach files so I'll just link to them.
If you find this useful please reply to this post. Feel free to modify and contribute as well.