Gi'day.
Karen
Reznek mentioned "bounced
mail"
in her note of Sat, 25 Aug 2001.
Lemme
share a recent quirk of ours.
I use a
commercial ISP, but our List
is out of
ASU. The two other ListOwners
are
located at ASU and the U of A.
For about
five weeks, I have been unable
to
communicate via my ISP to the U of A
Owner, but
I can communicate with ASU.
Not only
that, we: the ASU ListOwner
and I
received error messages about
the U of A
membership on our List.
----- The following addresses had transient non-fatal errors -----
<[log in to unmask]>
-----
Transcript of session follows -----
<[log in to unmask]>...
Deferred: Connection timed out with
cosmo.as.arizona.edu.
Warning:
message still undelivered after 4 hours
Will keep
trying until message is 5 days old
Not only
that, eventually our ListOwner at the U of A was
"un
subscribed", by Listserve, for all the accrued messages
not being
delivered.
I was
forced to request assistance from my
ISP
Customer Service. Eventually the problem was resolved,
here's the
explanation.
"To Mail Administrator:
I am the Senior System Administrator for (My ISP) and I
wanted to bring to your attention a problem with your <@Y.com>
mail
service.
I have recently upgraded our Linux mail server to the new 2.4.x
stable
Linux kernel.
The new Linux Kernel implements Explicit Congestion Notification - a
new
method defined in
(http://www.ietf.org/rfc/rfc2481.txt?number=2481)
RFC
2481 for improving TCP performance in the presence of
network congestion by allowing routers to provide an early warning
of
traffic flow problems.
Unfortunately, there are bugs in some Firewall products which cause
them
to reject incoming packets with ECN enabled. I believe your company
is
employing such a Firewall or packet filter on the public side of
your
primary MX record (mta.Y.com), thus you are rejecting legitimate
mail service from many, many sources.
Currently in our small ISP environment (<10,000 email users) we
have
queued over 40 messages destined for your mail server (mta.Y.com).
Below is a example of the mail Q listing -
##########################
f7OFBGL15955 2 Fri Aug 24 08:11
<[log in to unmask]>
(Deferred: Connection refused by mta.Y.com.)
<[log in to unmask]>
###########################
As you can see, the SMTP connect is refused from the Y mail server.
This mail server is running the Linux 2.4.x Kernel with Explicit
Congestive Notification enabled.
Fixes are available from some router vendors, and have been since at
least
mid-2000. These are not "feature patches" (which may add new
features and
have new bugs), but purely bug fixes, and thus should be safe to use,
even
for the most paranoid.
I will include some links with more relevant information for you to
review. I would be able to assist you in any fashion you would like
for
testing purposes.
RELATED LINKS:
Linux Kenel FAQ (Anchored to appropriate section)
http://www.tux.org/lkml/#s14-2
RFC 2481 (The official ECN Spec) <Please Obey>
http://www.ietf.org/rfc/rfc2481.txt?number=2481
Please let me know if it will be necessary for our ISP to
disable ECN from
our 2.4.x kernel because of non RFC compliance on the part of the
Excite
Network.
Thank you very much for your attention on this matter, I do
appreciate
your time."
Yes, the U
of A HAD installed a new Firewall - unidentified
manufacturer
and version so far.
I am now
able to communicate via e-mail with my
third
ListOwner. We had been telephoning about the
problem in
the mean-time. Once the Firewall was
corrected
he received a flood of mail which had been
building
up outside the gate.
Just
something else to keep in mind when you
receive
"bounced" messages from Listmembers.
Thank you
for your time.
Dave
J.