🚀 go-pugleaf

In article <davecb.725923251@yorku.ca> davecb@nexus.yorku.ca (David Collier-Brown) writes:
>  Your mail may be unreliable, but mine isn't: mine uses SMTP, which
>defines, as I already pointed out, a positive acknowlegement scheme
>FROM THE SENDING HOST TO THE RECIEVING HOST.

Sorry, I have to agree with John Stanley on this one.  In addition
to the scenario John mentioned, consider the following:

"user1@A" sends mail to "user2@B".  Mail for site B is handled by its
MX, C.  Therefore, site C is configured to handle all mail for B in
addition to its own.

1. user1@A's MUA hands off mail to A's MTA.
2. Site A's MTA connects to MTA at site C.
3. Site C receives mail, acknowleges its recept.
4. Site C's MTA connects to MTA at site B.
5. user2 dropped out of school and therefore is no longer a valid
   user at site B.  Site B nak's site C's delivery of mail with
   "user unknown".
6A. Due to a failure in the DNS configuration of site A, when site C
   tries to send a bounce to user1@A, it gets "host unknown" and
   site C promptly drops the bounce to the floor.
or
6B. Due to an improperly configured mailer at site A, the "From"
and/or "Reply-To" addresses are munged and unparseable.  Site C
drops bounce to the floor.
or
6C. Site C's /usr/spool/mqueue fills up and has insuffient disk space
in order to generate a bouce message.

What say you now?  Listen to John, you need to get out more.  SMTP may
be reliable, but SMTP is only a part of the picture, regardless of what
the pretty ASCII picture on page two of RFC821 says.  I suggest you
read the section "Reliable Mail Transmission" in RFC 1123, the
"Requirements for Internet Hosts".  Pay close attention to the words
"SHOULD" and "MUST".

--Dave
-- 
System Administrator, Population Research Institute    barr@pop.psu.edu
#define ENOTTY          25              /* Not a typewriter */