Hi, Our two outbound mail gateways have been blacklisted by Comcast, and the normal form (http://www.comcastsupport.com/Forms/NET/ blockedprovider.asp) is returning a weird error. See below. Your request for IP block removal has been denied for the following reason: - You have been blocked from emailing the Comcast network because we have determined that you are sending email from a dynamic/residential IP within the Comcast domain. Comcast does not allow subscribers to send email from a mail server other than smtp.comcast.net. All mail should be sent through Comcast's mail server. For information on configuring your machine to use smtp.comcast.net, please follow the link below. http://www.comcast.net/help/faq/index.jsp?faq=Email117481 Now, I'm pretty sure that our IP address block (147.9) is not part of Comcast, and we've been unable to get a hold of a person that can help explain this. Any help would be most appreciated. Thanks, Michael Grinnell Network Security Administrator The American University