Whenever a message cannot be delivered to a target mailbox (i.e. network down for too long, mailbox is full or removed, etc...) outside caller messages are forwarded to the UnaddressedMessages distribution list. By default the only member of this DL is the Example Administrator so you may need to pop open an Outlook profile for that account to fish the messages out.
The administration guide kinda harps at you to be sure you add someone "Real" to this distribution list for this reason. You'll want an admin type getting those messages so you can forward them as appropriate.
Jeff Lindborg
Unity Product Architect/Answer Monkey
Cisco Systems
jlindborg@activevoice.com
http://www.AnswerMonkey.net (new page for Unity support tools and scripts)