[Mimedefang] Re: lost input channel.

[Yizhar Hurwitz]

> Date: Wed, 20 Sep 2006 17:19:05 +0200
> From: "J.P van Oyen" <jeepee at gids.nl>
> Subject: [Mimedefang] lost input channel.
>
> In my sendmail logs I see so now an than entries like:
>
> Sep 17 20:46:00 www sm-mta[28696]: k8IKiuOO018686: lost input channel from
> ppp-104-23.telesat.com.co [200.71.104.23] to MTA after mail
>   

HI.


There are several possibles reasons for that.

One of them is a layer 3 network problem - MTU related.


One host is using PPPoE or similar connection that has an MTU of 1492.

As you can see by the name,

ppp-104-23.telesat.com.co

It might be the case.

The other host (your server) has MTU of 1500.

This can cause problems because PMTU doesn't work over some routers 
firewall that block ICMP .


Here is a nice article about this:

Path MTU Discovery:
http://www.sendmail.org/tips/pathmtu.html


If this is the case (or might be the case), possible 
solutions/workarounds are:

* ignore if it is rare and neglect able.

* Set your host MTU to 1492 instead of the default 1500.

* Disable PMTU on your server.

* Investigate further, for example check if you can see anything common 
to the hosts that cause this.


Yizhar Hurwitz

http://yizhar.mvps.org