Set PreferredDomainControler for Exchange Server 2010 by ADSIEDIT

Hi,

we have an Exchange Server 2010 SP2 Rollup 4.0 V02 which uses a Windows Server 2003 as LDAP- and GC Server. I'm not able to change the preferred DC by 'Set-ADServerSettings -PreferredServer DC01.contoso.com' to another DC (WS08 R2) on this Exchange Server! And the WS03 DC did not replicate with other 3 DC's since 7.Oct.2012.

Is there any other way than PS cmdlet and Exchange GUI to change the preferred DC? What about ADSIEDIT? Where does Exchange save the Infomation about his preferred DC and GC? If in Active Directory in which partition?

Thanks!

Regards,

Soheil