Re: [exim] Delivering Mail to Yahoo user

On Mon, Dec 21, 2015 at 03:55:46PM +0100, Marc Haber wrote:
> On Mon, 21 Dec 2015 16:19:18 +0300, Evgeniy Berdnikov <bd4@???>
> wrote:
> >On Mon, Dec 21, 2015 at 01:31:03PM +0100, Marc Haber wrote:
> >> On Mon, 21 Dec 2015 15:04:23 +0300, Odhiambo Washington
> >> <odhiambo@???> wrote:
> >> >2015-12-21 10:24:17 1a9cA9-0005Hu-3s == johnowino2000@???
> >> >R=outbound_throttled T=throttled_smtp defer (-18) H=mx-eu.mail.a
> >> >m0.yahoodns.net [188.125.69.79]: Remote host closed connection in response
> >> >to end of data
> >>
> >> Yahoo - a service provider too big to care for standards - is dropping
> >> your connection at a place where it should not do that without telling
> >> you why.
> >
> > IMHO, posted logs show indications of broken Path MTU Discovery.
> > Traffic dump between client and Yahoo relay may clarify this issue.
>
> If that would be the case, the SMTP session would most probably not
> get beyond the first block of DATA; and it would time out afterwards.
> In the current case, the remote host is actively ending the
> connection.

In the 3 posted examples there are two transmit timeouts on the
client side and one active connection close/reset from server side.
Both situations may be effects of PMTUD breakage.
--
Eugene Berdnikov