Subject: Re: 3.93 smtp-server design flaw/bug

From: Mike O'Connor <[email-masked]>
Date: Thu, 9 May 1996 09:17:20 GMT

In article <[email-masked]>,
Randall S. Winchester <[email-masked]> wrote:
:The snmp-server variable should be checking to see if there are valid MX

Oh oh...  an SNMP trap!  :)

:records for the name. It is unreasonable for users to have to know the list
:of MX records for a site or the preferences for this list. (aol.com has
:30...).

Not sure if "should" is the right word here...  mail punting can be
distinct from mail sending.  It's probably not a bad idea, but I
wouldn't see it as required behavior.  I may not want the email to
go through the backup MX records for the domain, especially if it
turns out to be unqualified or awaiting the proper qualification at
the SMTP server end for whatever reason.

:Also for the unix side, it would be nice if you could allow the mail message
:to queue locally if all the smtp server connection attempts fail.

Heh...  only makes sense if you happen to have sendmail running locally.
If I can limit where insecure MTAs run, I tend to want to do so.  

--
 Michael J. O'Connor                                 Internet: [email-masked]
 InterNIC WHOIS: MJO                                 http://www.coast.net/~mjo

"I propose we leave math to the machines and go play outside."         -Calvin

---

From: "Randall S. Winchester" <[email-masked]>
Date: Thu, 9 May 1996 11:42:16 -0400

On Thu, 9 May 1996, Mike O'Connor wrote:

: In article <[email-masked]>,
: Randall S. Winchester <[email-masked]> wrote:
: :The snmp-server variable should be checking to see if there are valid MX
: 
: Oh oh...  an SNMP trap!  :)
Opps... SMTP sorry.
: 
: :records for the name. It is unreasonable for users to have to know the list
: :of MX records for a site or the preferences for this list. (aol.com has
: :30...).
: 
: Not sure if "should" is the right word here...  mail punting can be
: distinct from mail sending.  It's probably not a bad idea, but I
: wouldn't see it as required behavior.  I may not want the email to
: go through the backup MX records for the domain, especially if it
: turns out to be unqualified or awaiting the proper qualification at
: the SMTP server end for whatever reason.

Proper use and maintainance of MX records is pretty much a requirement for
successful internet mail delivery.

As it stands now if you point your smtp-server at a machine with a valid MX
record which does not run sendmail in daemon mode, the message will not get
delivered. Also it you have 4 machines that all can accept mail for a site,
but only one of those hosts has an A record for that name, then Pine can not
take advanatage of the reliability that the redundent mailservers provides.
It will only deliver to that one host. This will most likely cause users
fits when need to leave for a class but can not deliver their mail message
because one machine is down.

I would like to have the smtp-server list point to sonmething like;
1st) ${department}.umd.edu ( a MX list for each depatrtments mailservers)
2nd) glue.umd.edu ( our toplevel MX'd list of servers as a fall back)

: 
: :Also for the unix side, it would be nice if you could allow the mail message
: :to queue locally if all the smtp server connection attempts fail.
: 
: Heh...  only makes sense if you happen to have sendmail running locally.
: If I can limit where insecure MTAs run, I tend to want to do so.  

Actually it makes sence when you do not either. I have about 800 Unix boxes
and only run sendmail (in deamon mode) on about 40 of them. Sendmail still
gets execed on the clients, and I have to check for things in the queue
every 30 minutes, but they do not accept connections. Most every other mail
application needs this capability.

That pine has the ability to connect directly to an SMTP server is nice, but 
it should do it with similar robustness of things like "sendmail" that it is
trying to skirt. (i.e. understand MX records)

I conced that some of these may be switched options, but they really should
be part of the code base.

As an aside, this same poor behaviour with eudora has been sysadmins bain
for years. You have to go and reconfigure thousands of PC's every time you
make changes to ths smtp servers. I would hope that Pine could do one step
better and support MX records for smtp-servers on PC's also.

Thanks for listening,
Randall

: 
: --
:  Michael J. O'Connor                                 Internet: [email-masked]
:  InterNIC WHOIS: MJO                                 http://www.coast.net/~mjo
: 
: "I propose we leave math to the machines and go play outside."         -Calvin
: 
:

---

From: Steve Hubert <[email-masked]>
Date: Fri, 10 May 1996 09:45:26 -0700 (PDT)

On Thu, 9 May 1996, Randall S. Winchester wrote:

We don't agree with your interpretation of the purpose of MX records.  MX
records are intended to be used for routing mail to a destination, not for
routing an SMTP connection to an initial dropoff point.  I would consider
it a bug if pine did what you suggest.  For example, it would be
reasonable to have a domain called smtpserver.something that is intended
to be an outgoing SMTP server for random Netscapes, Pines, and other
mailers.  It would also be reasonable for smtpserver.something to have an
MX record pointing somewhere else so that mail sent to
[email-masked] gets routed to a host that accepts incoming
mail instead of going to smtpserver where there are no users and no
logins.

> successful internet mail delivery.

We agree on this.

> because one machine is down.

You can have more than one smtp-server in the list, but I think you
already knew that.

> [deleted]

We're not trying to skirt sendmail, we're just trying to give it to a
sendmail (or other smtp server) so that that MTA can handle the routing
for us.  If we were really trying to skirt sendmail we wouldn't deliver to
smtp-server, we would look up the MX of the recipients of the message and
try to deliver directly to them.  But we're not trying to deliver it,
we're just trying to pass it off to some MTA to deliver it for us.
 
> be part of the code base.

We'll think about adding an option.

> better and support MX records for smtp-servers on PC's also.

Instead of changing thousands of PCs, how about using some indirection in
DNS?  For example, you could define smtpserver1, smtpserver2, ... to be
CNAMEs pointing to whatever servers you wanted.  If all the PCs were
configured to use those names, you'd only have to change those DNS entries
to cause a change to happen on the thousands of PCs.

> Randall

Thank you for this discussion and your other suggestions.

Steve Hubert <[email-masked]>
Networks and Distributed Computing, Univ. of Washington, Seattle