sgifford at suspectclass
Nov 7, 2007, 7:57 AM
Post #2 of 2
(647 views)
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Nikola Vladov <v20-qd-1195053307xoheufd [at] riemann> writes:
> Seems, that DJB does greylisting on cr.yp.to (port 25)
> On the first attept he refuses the connection after 100 sec.
> On the seond pass (qmail make it in 7 min) it accept it.
>
> I understand this as: DJB like greylisting!
> I post this to check my conjecture.
I don't see this behavior from here.
One possibility is that tcpserver is configured to get DNS data from
the connecting IP address, and requests for that information are
timing out. If that's the case, the first time it will take a long
time to start qmail-smtpd, but after that the negative result will be
cached and so it will go much faster. I believe the normal timeout
for the SMTP greeting will be long enough to tolerate this, but if
your server is configured with a shorter timeout you could see this
effect.
---Scott.
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