You must install the Exchange System Manager on the Backup Server to backup Exchange Server. It is possible to backup the Exchange Server without Exchange System Manager with the following trick:
Copy ESEBCLI2.DLL from the Exchange 2003 CD into the EXCHSRVR\BIN folder
Add the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\BackupRestore\DLLPaths – REG_EXPAND_SZ – esebcli2 – c:\exchsrvr\bin\esebcli2.dll.
After modifying the registry you can use NTBACKUP to backup the remote Exchange Server by clicking – Tools – Remote Store.