[H-GEN] sendmail timeout problem

Bruce Campbell bc at humbug.org.au
Fri Dec 12 05:34:36 EST 2003


On Thu, 11 Dec 2003, Robert Brockway wrote:

> On Fri, 12 Dec 2003 johannes at paradise.net.nz wrote:
>
> > Running sendmail 8.11.6 essentially works just fine except a couple of domains
> > do consistently time out with the message "Deferred: Connection timed out
> > with smtp.domain, or smtp2.domain"
>
> Try this:
>
> cat /proc/sys/net/ipv4/tcp_ecn
>
> If you get a 1 come back, then set it to be 0:
>
> echo 0 > /proc/sys/net/ipv4/tcp_ecn
>
> If you use ecn some remote routers will go gaga on you.  I've seen this
> exhibit as "truly bizarre" mail problems.

Its more the age of ACLs on said remote routers/firewalls, some of which
predate the creation of ECN, and still think that using those 'reserved'
bits in TCP is an indication of someone trying something nasty.

Conversely, certain ECN implementations (for example, Linux) do not seem
to be liberal in what they accept, and do not attempt to retry the
connection sans ECN should the ECN attempt disappear[1] into a black hole.

--==--
Bruce.

[1] As distinct from retrying due to a 'not supported' or equivilant
    packet coming back.



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