[wplug] users sending to wrong email address

Bill Moran wmoran at potentialtech.com
Thu Jan 3 11:40:53 EST 2008


In response to Kevin Squire <gentgeen at linuxmail.org>:

> 
> I am running the school's email server. Due to PEBKAC I see a lot of
> this:
>   connect to pavcs.blackboard.org[66.246.195.42]: Connection timed out
> 
> Seems as though many of our users are trying to email
> USERNAME at pavcs.blackboard.org when it should be a .com
> 
> The server does it's job, and tries to connect, even tries a few times,
> then of course, times out cause blackboard.org is just a "page squatter"
>  
> 
> I was wondering if I could edit my /etc/hosts file on the mail server
> (that is all it is - a mail server) to point pavcs.blackboard.org to an
> internal machine ... or some other solution to speed up (and therefore
> reduce load) the "timed out" message.  
> 
> I still want users to get the error message... let them know they are
> doing something wrong - so simply redirecting is not OK in this case. 
> Just want to speed the process along some.

Linux, right?  If so, you'll have ipchains or iptables or ipchairs or
whatever it is available to you.

<rant>
First off, pavcs.blackboard.org is misconfigured.  I'm sick and tired
of people setting up packet dropping firewalls all over the internet.
TCP connections to closed ports should return RST.  Sysadmins who don't
should be drawn and quartered.
</rant>

You can simulate this by installing a packet filter rule on your mail
server that returns RST when outgoing connections to that IP are
attempted.  It will cause sendmail to immediately abandon the
connection and put the email in the deferred queue, thus reducing your
overall socket usage.

I'm curious ... is the instance of this particular email server so much
higher than all the others that it deserves special attention?

-- 
Bill Moran
http://www.potentialtech.com


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