For the past 1 month we've been troubleshooting an issue with our SCOM and Exchange 2010 monitoring.
The monitonring with the SCOM Management Pack works fine for a long time, but suddenly the extest_ account get locked out. This is right after the automatic password change routine on the Exteset_ account.
After talking to MS premier support, they have now found a bug in how the SCOM does it authentication, and that the authentication is multiple ways.
I've got an workaround, and that was to disable the following SCOM monitors, this did not work for us, but you might try it to remove the annoying SCOM alerts. This is the response we got from Microsoft:
"In the authoring section of the OpsMgr console, “Outlook Server Availability” to your scope and disable the 6 monitors that start with “KHI: HTTP Connectivity Against Local Server”. This should disable the instance of test-outlookconnectivity that causes this problem. We’ll be addressing issue, but this should serve as a workaround for now"