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From: dbfunk@icaen.uiowa.edu (David B Funk)
Newsgroups: comp.mail.sendmail
Subject: Re: addressing priority
Summary: internet vs UUCP addressing format
Message-ID: <4018@ns-mx.uiowa.edu>
Date: 19 Jan 91 06:57:16 GMT
References: <2505@sapwdf.UUCP>
Sender: news@ns-mx.uiowa.edu
Organization: Iowa Computer Aided Engineering Network, University of Iowa
Lines: 40

In article <2505@sapwdf.UUCP> Bill Wohler <wohler@sap-ag.de> writes:
>
>  i was under the impression that internet addressing took priority.
>  that is, an address like hosta!user@hostb would be sent to hostb
>  first.
>  the sendmail.cf's around here send such a message to hosta first.
>  is this correct?  if not, what section of sendmail.cf should i look
>  at.  if so, how can i modify the address so that the message goes to
>  hostb first?  what is the current rfc number that covers this
>  issue?
>

  There are 2 general formats of e-mail addresses, internet & UUCP.
(the less said about Berknet & route addrs, the better 8-)
Assuming that you have mail that needs to be routed through 1 system
(say hosta) to be delivered to a user on a second system (say hostb)
then the addresses would look like:

Internet:   user%hostb@hosta

UUCP:       hosta!hostb!user

Both of these formats can be extended to arbitrarily long paths in an
unambiguous manner ( user%hostc%hostb@hosta & hosta!hostb!hostc!user ).
  As both are unambiguous valid address, it is possible to create rule
sets that will automatically convert from one form to the other.
Ideally, a sendmail should handle both of these addresses and consider
them equivalent.

  The address example from the posting "hosta!user@hostb" is a misfit
mish-mosh address that has parts of internet & UUCP combined. As the
poster found, it is ambiguous, and can be interpreted in 2 different
ways, depending upon the site conventions. This address form should be
avoided and its use discouraged.
  So in answer to the question, the address should be converted to one
of the above mentioned formats which will then force the desired
interpretation. IE  hosta!user@hostb => user%hosta@hostb should force
the interpretation of "send it to hostb for delivery to user on hosta".

Dave Funk