12800 events indicate you are running out of memory. For example:
Event Type: Error
Event Source: MSExchangeIS
Event Category: Content Engine
Event ID: 12800
Time: 9:47:14 AM
Message processing failed because there is not enough available memory (8007000E-80000000).
There are three basic courses that troubleshooting can follow here:
- Check for 9582 events. If you have them start with these: Collect performance data, make sure the updates from KB article http://support.microsoft.com/kb/960144 are applied, and follow the steps in http://support.microsoft.com/kb/325044
- If there are no 9582 events in your application log turn up Diagnostic logging on MSExchangeIS\Content Engine (this should generate 9684 events for bad calendar items)
- Use the CalCheck tool described in this blog: http://blogs.technet.com/b/exchange/archive/2012/02/22/calcheck-the-outlook-calendar-checking-tool.aspx
The CalCheck tool has resolved a couple of these cases for me since it was released. In these cases bad calendar items were blowing right through the limits that Exchange had imposed upon their conversion. The conversion engine had only allocated a fixed amount of RAM and these items required more. This caused the Out of Memory error to be reported. When CalCheck examined these items it flagged them. When the Administrator deleted them the 12800 events disappeared from the application logs of the Exchange Server.
Hopefully Randy's CalCheck tool will be equally effective for you if your server is encountering this event. The tool should be good for locating bad calendar items whether you have the 9582 events or not. In fact, once the bad calendar items are cleared out, it may lessen the 9582 events. Just be careful not to assume that it will lessen or stop them. The abbreviated steps I provided in the first bullet point are still your best bet if you are seeing 9582s.