On Wed, 3 Mar 2004 07:15:05 +0000
Matthew Seaman <[EMAIL PROTECTED]> wrote:

> On Tue, Mar 02, 2004 at 08:11:36PM -0500, Justin Brody wrote:
> > A couple pieces of information that might be relevant:
> > About a month ago, I was running the same FBSD version with the
> > same sendmail.cf from behind a different router connected to a
> > different cable modem and calling my box "cogito.none.org".  This
> > seemed to work o.k.
> After sleeping on it, I'm starting to think that the problem is not
> actually within the SMTP setup, but is rather something to do with
> firewalling or similar measures.  Does your ISP permit you to run SMTP
> servers? Many have been bitten very badly by clueless windows users,
> and so deny use of SMTP to all.  Sometime this proscription also
> extends to enforcement by transparent proxying or other measures to
> control SMTP traffic from their clients.  You should check with them
> as to what their policy is.
> Can you telnet to port 25 on the UMD server or the ISP's server you're
> trying to connect to?  If you can't get a connection established, I'd
> suspect the problem is firewalling somewhere between you and them.
>       Cheers,
>       Matthew
> -- 
> Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
>                                                       Savill Way
> PGP: http://www.infracaninophile.co.uk/pgpkey         Marlow
> Tel: +44 1628 476614                                  Bucks., SL7 1TH
> UK

FWIW I once had similar problems properly sending mail to a particular
ISP mail server (it would timeout just like this one but work fine for
other destination mail servers). Manually running the queue in verbose
mode would indicate that it was connecting properly but hanging at the
data send stage until timing out about five minutes later. Had me
baffled because I had been connecting to that server maybe two weeks
before without a hitch and hadn't changed my sendmail config in that

After searching google and pouring through the FAQ and other docs at
sendmail.org I found a reference to possibly misconfigured intermediary
routers not handling the icmp packets on which the PMTU Discovery
feature needs to work properly (set by default on both FBSD and OBSD I
believe). I disabled PMTU Discovery in /etc/sysctl.conf on my gateway
host and through some ping tests derived 1404 as the optimal PMTU (I'm
on a DSL connection) between my site and the troublesome mail server. I
set this number manually for the outgoing interface on my gateway
through an ifconfig parameter and the problem disappeared. I have been
able to connect properly to that mail server ever since.

Just another potential avenue to investigate...


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