How can you test routing paths (traceroute, MX lookup)?

Start with MX lookups to see where mail should go. Use dig or nslookup to query MX records: dig MX example.com shows the mail servers and their priorities for a domain. This reveals the intended destination before you send anything.

Test SMTP connectivity with tools like telnet or swaks. Connecting to port 25 or 587 on the target server lets you simulate the SMTP handshake and see how the server responds to your sending IP. You'll discover if connections are accepted, rejected, or deferred.

After sending, analyze email headers. The Received headers show every server that handled the message, in reverse order. Tools like Google Admin Toolbox or MXToolbox Header Analyzer parse these into readable timelines showing the path your message traveled.

Chart the waters before you sail, then check the log after arrival. Both reveal whether the route ran true.

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