Exchange 2000 anonymouse mail

Hi, I have a client that has just upgraded to Exchange2000 running SBS

They need to allow mail with no know recipitent to be delivered to a general mailbox. Their web site is generating addresses within their domain but the mailboxes don't exisit. They have 3000+ adresses that are now without mailboxes. This is growing daily. Is there a way to have undeliverable mail sent to a holding mailbox rather than refused?

Any other suggestions are also welcom.

Paul H.