exchange 2003 clean up agent的作用。

The tool scans the mailbox store to ensure that all of the mailboxes have associated domain accounts. If they do not then the mailbox is marked with a red cross, and eventually deleted.

Once the red cross is on the mailbox you have two options.

1. If you have deleted an account by accident then you can reattach it by right clicking on this orphaned mailbox and choose Reconnect.  
2. If you want to get rid of the mailbox totally, right click on the mailbox and select Purge will remove it.

If you right click on an account without the red cross, the reconnect and purge options are disabled.

It plays no part in cleaning up the mailbox content.

It runs as part of online maintenance each night.

http://www.microsoft.com/technet/prodtechnol/exchange/2003/insider/exstoremaintain.mspx