Christian Vogel correctly suggested:
>
>On Wed, Sep 24, 2003 at 04:24:02PM -0700, Michael Coxe wrote:
>> I've searched the Exim archives & Usenet regarding an Exim error
>> message when certain hosts attempt delivery to my mailserver.
>> For example (the namedroppers mailing list):
>>
>> SMTP data timeout (message abandoned) on connection from psg.com [147.28.0.62]
>>
>> The concensus is that the error is genaerally caused by a firewall
>> or other such device. In may case (home environment), it might be
>> my DSL box/firewall, a ZyXEL model Prestige 643.
>
>You could try to disable path mtu discovery[1] on the mailserver
>and see if this fixes your problem. If it does, try to find the broken
>or misconfigured router/firewall that swallows the ICMP-unreachable
>packets. Increasing timeouts will *not* work around
>the problem because the (overly big) packets are never received by
>one of the hosts.
>
>[1]: Linux: echo 1 >/proc/sys/net/ipv4/ip_no_pmtu_disc
> BSD/Cisco/...: http://www.netheaven.com/pmtu.html
Christian's pointers lead me to the answer, that my DSL box uses PPPoE
with it's 8-byte overhead and thus trouble with 1500 byte packets. The
Netheaven.COM link explaims the issue quite well. I reduced my MTU to
1492 and haven't had a SMTP data timeout since.
- michael
