All, I have just noticed the following in the event viewer, can anybody shed any light on the matter? Event Type: Error Event Source: MSExchangeTransport Event Category: NDR Event ID: 3030 Date: 03/02/2004 Time: 15:35:34 User: N/A Computer: JUPITER Description: A non-delivery report with a status code of 5.1.8 was generated for recipient rfc822;joe@xxxxxxxxxxxxxxxxxx (Message-ID <168401c3ea6b$5ad73780$02010a0a@xxxxxxxxxxxx>). Have checked on google groups, eventid.net and microsoft to no success. Setup as follows Windows 2003 (patched upto date) Exchange 2003 (patched upto date) Sophos Anti Virus - Mail monitor (up to date) Many Thanks Simon