On Tue, May 15, 2007 at 14:11:44 +0200, joeri Belis wrote:
>
> I get the same issue with "skynet.be" domain. According to there support,
> only accept 4 connections / second.
>
> deferral:
> Connected_to_xx.xx.xx.xx_but_greeting_failed./Remote_host_said:_421_#4.4.5_T
> oo_many_connections_from_your_host./
>
> and then Connected_to_XX.XX.XX.XX_but_connection_died._(#4.4.2)
>
> would the concurrencyremote be an solution.
Yes. A bad one.
That is, do not make concurrencyremote very small
to "work around" this "problem".
There are patches for qmail-remote which limit concurrency
per destination IP address:
http://www.coyotetechnical.com/software/patches/qmail-send-concurrencyperip.patch
But skynet.be does limiting based on connections per time interval.
So even if you make concurrencyperip 1, you can still easily reach 4 conn/s.
But do not worry, qmail retries later.
As you can read, error was 421, not 5xx.
SMTP protocol does not provide feature for inquiring SMTP server's
concurrency or other resource usage limits, so all it can do is
return 4xx error. And perhaps a descriptive reason for it.
If you use Linux 2.6, you can use hashlimit to limit connections to
skynet.be... Just DROP the SYN packets, next packet might get thru
(it tries to connect several [1] times in 60 seconds [2]).
[1] sysctl net.ipv4.tcp_syn_retries
[2] control/timeoutconnect
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