I think I have the problem, look at this: (Posted here: http://www.nicva.org/index.cfm/section/General/key/190805DupEmails ) The problem An email from our chief executive was sent to around 300 recipients on Thursday 18 August. One of the recipients of this email had failed to add a critical software update to their computer. The result was that their machine duplicated the email from us and resent it many times to all the email addresses in the original list. This is due to a known problem with Microsoft software. Microsoft has provided an update for Windows Small Business Server 2003: KB 835734 on their website. Patch is on : http://www.microsoft.com/downloads/details.aspx?FamilyId=7B1FF109-092E-4418-AA37-A53AF7B8F6FC&displaylang=en I just need to trace the unpatched client, and contact their own IT staff.