I've had conversations in the past as to wether or not the computer account belonging to an Exchange 200x server can be moved between OU's. This can be the case if you add the server to the domain before creating the computer account. This causes the computer account to be created in the default computers OU. Another scenario is the restructuring of OU's either for security or Group Policy administration. Whatever the scenario is, the answer is that the Exchange computer account can be moved, but the System Attendant generates Event ID 9186 and Event ID 9187 errors. The KB article below explains how to resolve this.
http://support.microsoft.com/default.aspx?scid=kb;en-us;271335&sd=ee
Teo
