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.TH MAILPATH 1 "19 July 1988"
.SH NAME
mailpath \- show what the mailer thinks of an address
.SH SYNOPSIS
mailpath domainname
.SH DESCRIPTION
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.
.SH PARAMETERS
.IP "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.
.SH EXAMPLES
Some possible outputs from mailpath are illustrated below:
.RS
% mailpath yahoo.uucp
.br
.nf
Error: Unresolvable address: user@yahoo.uucp
.fi
.RE
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.
.RS
.br
.nf
% mailpath yahoo.bitnet
Ok: SMTP connection to one of (ugw.utcs.utoronto.ca gpu.utcs.utoronto.ca)
.fi
.RE
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.
.RS
.br
.nf
% mailpath csri
Ok: SMTP connection to yonge.csri.toronto.edu
.fi
.RE
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:
.RS
.br
.nf
% mailpath felix.uucp
Ok: UUCP path selected: uunet!spsd!felix!user
.fi
.RE
The current UUCP database contains the only data about felix, and the
route last advertized for that site is the one returned.
.SH NOTES
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.
.SH LIMITATIONS
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.
.SH "SEE ALSO"
sendmail(8), uupath(1), uushow(1)
.SH "AUTHORS"
Cooked up iteratively by Jean-Francois Lamy and Rayan Zachariassen,
Computer Science, University of Toronto.
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