Tool for internet mail tracking?

You have two separate issues going on here. First issue is whether the email moved on successfully. The way SMTP works, the sender at each stage gets an acknowledgement of receipt from the next stage. For the client, the outbox goes empty. For mail servers, the email leaves the queue only after the receipt comes in. A simple data analyzer can watch this, as the codes are all identified in the RFC. See http://www.tac.nyc.ny.us/mail/rfc-index.html for the list of applicable RFC and Standards.

Moving towards the destination, the header has the path appended to it. This is why you can look at the header of received mail and trace it back to the source. However, there is no mechanism like ICMP (trace route) to respond to the originator at each hop. The protocol was never designed with that functionality in mind.

It's a pretty good all in one resource for e-mail detective bits. :)

for the tool (Windows):

http://www.samspade.org/ssw/

Truncate it for the Homepage:

http://www.samspade.org

:)