An email gateway diagnostic, tool, system, and method are provided for automated troubleshooting of email gateway functionality. Troubleshooting can occur in multiple modes of operation including: full diagnostic, interactive, and undeliverable mail status information. Based upon a set of rules and conditional statements, network and email gateway configurations, and user responses, an automated troubleshooting tool performs necessary testing to the email and network systems to interpret the available information and present the user with the source of the problem or suggest solutions and make recommendations as to why the email gateway may not be functioning properly.