I am the Exchange postmaster of my company and I receive all incoming mail being sent to NON-existing accounts with an "Notification: Inbound Mail Failure" Message. Most of these are unsolicited spam mail from *@yahoo.com accounts and cannot be replied to. My first question is why are they coming through at all when the person they are emailing does not have an email address. My second question is how to block these. I don't want to totally block all mail from yahoo.com. Thanks for any assistance. Marie L. Spaulding IT Administrator ASE Americas, Inc. 4 Suburban Park Drive Billerica, MA 01821 978.947.5967 (phone) 978.663.7555 (fax) mspaulding@xxxxxxxxx