[Techtalk] Null connections with sendmail?

[Raven, corporate courtesan]

Heya --

Quoth Michelle Murrain (Wed, Mar 27, 2002 at 09:08:29AM -0500):
> Mar 26 16:03:46 nanuuq sendmail[22722]: NOQUEUE: Null connection from 
> lax1evtmx2.citysearch.com [209.104.61.11]
> 
> I looked at mail logs previous to the move, and there are a few of these, 
> but far, far fewer than there are now. In addition, it appears that some 
> people have intermittent mail delays (some mail takes 12 hours to deliver, 
> instead of a couple of minutes.)

>From the sendmail FAQ: (http://www.sendmail.org/faq/section4.html#4.18)

Subject: Q4.18 -- What does "NOQUEUE: Null connection from ..." mean?

Date: February 24, 2000 
Updated: March 12, 2000 

An entry like: 

NOQUEUE: Null connection from host.domain [IP.AD.DD.RESS]

in the logfile means that host.domain connected to your MTA but neither
initiated transmission of a message (by issuing the MAIL command), nor
used any of the commands that are logged separately (EXPN/VRFY/ETRN).
Unless this happens very often, you can ignore this.  If it happens very
often, it's either someone playing around or it's a network problem. 

Note 1: The significant part of the message isn't the NOQUEUE, but the
"Null connection from ...". In particular, NOQUEUE isn't an error
indication, but just a "place-holder" when no queue ID has been
assigned, typically because message collection hasn't started (yet). It
can occur in other messages too, and there too the significant part is
what comes after the NOQUEUE. 

*********

	So first, check out the connectivity on your new network.  It's
possible that these connections are being dropped between the time when
they were opened and the time when they were (supposed to) send mail to
you.  Tcpdump it if you have to -- you should see the drops and the
retransmissions.

	If you're not having any connectivity problems, I'd try keeping
track of where the null connections are to.  If it's always one
particular server, then it might be connection problems (or monkeying)
on their side.  But since people are having problems getting mail to you
for 12 hours or more, I'd be tempted to suspect the connectivity on your
end, particularly if there are only problems when sending through your
server.  
 
> Ideas? Are these connected?

	Yep.  Bad connectivity = repeated tries and long delays when
trying to get mail.  Hope that helps, and good luck tracking down your
network problem.

Cheers,
Raven 
 
"That should be: "If cryptography is outlawed, only bhgynjf jvyy unir
 pelcgb!" Or maybe, for maximum effect, "...only pvumbxt xjmm ibwf
 dszqup!""
 -- Kai, on 'better' cryptography

MD5 (outlaws) = 4c86ccf216da19edcc4b80e3824b67ab
 -- my response