Some of the mailboxes are not getting synchronized and a message similar to the following is posted to the Mail Target Agent log:
"CMBMConn::CheckHomeStore Warning 4813 Cannot log on to mailbox '/o=Organization/ou=HQ/cn=Recipients/cn=JohnSmith' until the Active Directory replication cycle completes. The agent will attempt to log on to this mailbox again during the next session."
This warning is normally indicating issues with the associated domain controller or replication problems. Another possible reason for this warning is that the mailbox is in the process of being moved. A third possibility is that the mailbox has been switched, moved to another store by Exchange native tools, and a resync is being attempted pointing to the original store.
1. In Project Manager on the Exchange Data tab, expand the Target Exchange 200x Organizations down to the Exchange server where the Mail Target Agent (MTA) is installed.
2. Right-click the server, select Properties and see General | Associated domain controller page.
3. Verify that the domain controller listed there is operational, responds to LDAP queries and is located in the same site with the target Exchange server.
In some cases rebooting the target Exchange server where the MTA is running proved to be a resolution.
On the mailbox resync collection, right click and select Properties. Make sure that the "Select the Mailbox Store for the Exchange 200x mailboxes:" contains the store where the mailboxes reside now and not the original location where the mailboxes were first created.
Remove Outlook from the server hosting the mail target agent and reboot.