We upgraded our mail server recently to Microsoft Exchange 2007 and users started experiencing problem sending emails to multiple recipients on same domain. The error message: Diagnostic information for administrators: Generating server: exchange-server.internal.domain.com [email protected] external.mail.server.domain.com #500 Firewall Error ## The error message is pretty clear as to where the problem lies. We do have cisco… Continue reading Email Server Generates “#500 Firewall Error##” Error