mailpath - show what the mailer thinks of an address

mailpath domainname

This program takes an address and shows how the mailer would interpret it. This is useful to determine if a strange domain is actually recognized by the local software. Some routing information is also given when available (most of the time a direct connection to a gateway is used and it is the gateway's responsibility to do further routing).

By contrast, uupath(1) returns data from only one of the databases queried by the mailer. mailpath output reflects the actual decision the mailer would take based on all available databases and conflict-resolution rules.

domainname

This is normally the right hand side of a user@domain address. Examples of such domains include jazz.db, ibm.com, uunet.uu.net, ubc.ca, utoronto.bitnet, or mcvax.cwi.nl. You should try those names to see what mailpath produces as output.

As a convenience, mailpath will try to do something sensible with user@domain and sitea!siteb!user.

Some possible outputs from mailpath are illustrated below:

% mailpath yahoo.uucp

Error: Unresolvable address: user@yahoo.uucp

In this particular case, the mailer knows for sure that it can't deal with the address; a message sent to that destination would bounce right away.

% mailpath yahoo.bitnet
Ok: SMTP connection to one of (ugw.utcs.utoronto.ca gpu.utcs.utoronto.ca)

Note that in this case there is no such machine as yahoo.bitnet, but that the mailer can't actually tell. All it knows is that any mail for a site claimed to be under BITNET will be handled by one of the two campus gateways listed. A message sent to yahoo.bitnet would be sent to whichever is available, and would bounce there when they look up yahoo in their official BITNET tables and don't find it. In other words, the fact that mailpath returns an "Ok" indication is no guarantee that a site later on won't find something wrong with the address.

% mailpath csri
Ok: SMTP connection to yonge.csri.toronto.edu

In this case, one can see that the local mailer considers csri to be synonymous with yonge.csri.toronto.edu, as far as mail delivery is concerned.

Some indication of the route taken can often be gleaned from the output of mailpath:

% mailpath felix.uucp
Ok: UUCP path selected: uunet!spsd!felix!user

The fact that mailpath returns something is not an indication that the machine actually exists, but merely that the mailer has found a way to deal with the message (often by punting it to someone else). Therefore the main use of mailpath is to check that, say, user@mcvax.cwi.nl makes some sense and that the message go somewhere else.

Garbage in, garbage out. The routing data for UUCP is updated monthly, but sites are under no obligation to keep up-to-date. Therefore the route computed by mailpath or uupath(1) may in reality not be usable.

It would be nice if the gateway selected for delegation could be shown, but this information is not available in the router output output.

sendmail(8), uupath(1), uushow(1)

Cooked up iteratively by Jean-Francois Lamy and Rayan Zachariassen, Computer Science, University of Toronto.