When you use the Inter-Organization Replication tool (IORepl) to replicate public folder and free-and-busy information between two Exchange Server 2003 organizations, replication may not be completed successfully. Additionally, if logging for the replication session is turned on, the following message will appear in the logs:
WARNING: Unable to open another MAPI session to server Server Name to replicate Free/Busy site 'EX:/o=Organization Name/ou=Organizational Unit Name on server Server Name, skipping.
This issue may occur if the replication session does not log on to one of the Exchange Server 2003 computers.
To resolve this issue, make sure that the public message database (.mdb) and the private message database that your MAPI session logs on to are on the same server.