LDP.exe is a useful tool for querying information out of Active Directory, in particular performing searches.
To perform a search using LDP.exe perform the following actions:
1. Open LDP.exe, go to connection and click Connect. Type in the address of one of your domain controllers.
2. Click connect and go to bindings. Enter a user name, password and domain name to which you want to connect with.
3. Click Browse and then click Search. In Base Dn enter the location in which you want to start searching from. Under filter type in a filter, I said any objects in active directory containing the msExchHomeServerName attribute, and if the attribute contains anything return the results. Also click subtree, this means it will search all recursive tree's in the LDAP structure.
4. Click Options. Under Attributes specify which attributes you want to return for each object found meeting your search query.
Perform the search, very easy!
Microsoft KB224543 has lots more information about this: