jethro.binks at strath
Jun 19, 2012, 5:37 AM
Post #1 of 6
I've been having an ongoing discussion with a supplier about their
Delays, timeouts, and conflict
inability to send us email.
Here's a summary of one of the transactions:
2012-05-31T18:47:44+01:00 SMTP connection from [126.96.36.199]:48322
I=[188.8.131.52]:25 (TCP/IP connection count = 79)
2012-05-31T18:48:31+01:00 Noting recipient:
(Extra log message we add when recipient sent)
2012-05-31T18:49:21+01:00 SMTP connection from mailout28.mail01.mtsvc.net
(n08.mail01.mtsvc.net) [184.108.40.206]:48322 I=[220.127.116.11]:25 lost
while reading message data (header)
We impose various delays in the SMTP transactions. To my reading of these
log messages, the remote side is dropping the connection some time after
sending the first RCPT, but before DATA session is complete.
The sending server is apparently Exim, according to the support staff for
the providers (mtsvc.net): "Unfortunately, we have no solution when
sending email to "strath.ac.uk" email servers from your (gs) Grid-Service.
I have not seen this problem happen to any other customers on the (gs)
Grid-Service and when connecting to the server using basic telnet
commands, the response time from their server is very slow. I understand
they implemented policies to combat spam, however our Exim configurations
are standard and as I stated working for thousands and thousands of users
on our shared email product.".
DELAY_SMTP_RCPT_FIRST = 30s
DELAY_SMTP_DATA = 30s
which are implemented near the start of the relevant ACLs (hosts in dnswl
are exempt from the DATA delay)
So I have a couple of questions really:
1. is my reading of the reason for the failure to transfer correct, or
could there be another cause that requires deeper investigation?
2. do other sites see issues from this particular set of sources,
particularly if you are imposing delays?
The fine manual found for me the settings which the remote host might have
adjusted (smtp transport, "data_timeout", "command_timeout", etc), so I
guess I could ask for them to report what those values are set to, if they
will be willing to disclose them. It may be that they are not aware that
these parameters are adjusted from the defaults, but I'm wary that I've
Anyway, my choices appear to be to convince them that their Exim is
ill-configured and push them in the direction of how to fix it, if that's
what it is, or make a special exemption for the sending hosts. This
latter course of action I always consider a last resort, at least when I
have some sort of standards-based reason to support me for refusing to do
so. Which is why I need a sanity check on my logic!
. . . . . . . . . . . . . . . . . . . . . . . . .
Jethro R Binks, Network Manager,
Information Services Directorate, University Of Strathclyde, Glasgow, UK
The University of Strathclyde is a charitable body, registered in
Scotland, number SC015263.
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