In Exchange 2003, Administrator accounts are denied access to mailboxes. As such, the EXMERGE utility will fail to export mailboxes when run using the Administrator account. To enable the Administrator account to use EXMERGE for exporting user mailboxes in archival situations, the following fix must be applied.
Open Server Management, browse to Advanced Management, First Organization (Exhcange), Servers, [servername]
Right Click on the server name, and select properties.
Select the Security Tab, and click the Advanced Button.
Untick the Check Box, Select Copy. Then select all Deny Permission Types, and click Remove.
EXMERGE should now run properly.