CSCatchAll adds a much-needed feature to MS Exchange Server 2000 and 2003: A catch-all mailbox that receives all mail originally addressed to recipients that are not in your active directory. There is zero configuration of CSCatchAll necessary - just install it and add a "catchall@yourdomain.com" email address to any of your users in the active directory. That user then receives all misaddressed email.
This feature is very useful if you do not want to emit non-delivery reports back to the sender and still want to keep your normal email addresses. CSCatchAll only reroutes those emails that can not be matched to any regular recipient in your organization.