mrichter@CL-LINUX-3OG-MR:~$ telnet mxzhh.bluewin.ch 25 Trying 195.186.227.50... Connected to mxzhh.bluewin.ch. Escape character is '^]'. 421 4.4.5 Service unavailable, concurrency limit reached. Connection closed by foreign host.
Trying 195.186.227.50... telnet: connect to address 195.186.227.50: Connection refused telnet: Unable to connect to remote host
This with all 3 MX:
bluewin.ch. 88 IN MX 10 mxbw.bluewin.ch. bluewin.ch. 88 IN MX 42 mxzhb.bluewin.ch. bluewin.ch. 88 IN MX 42 mxzhh.bluewin.ch.
Freundliche Grüsse
sasag Kabelkommunikation AG Michael Richter Professional Bachelor ODEC in Engineering mrichter@sasag.ch 052 633 01 71
Yep, seeing the same error messages in our logs:
195.186.99.50 [06B0] 10:01:08 Client session <<< 421 4.4.5 Service unavailable, concurrency limit reached.
Regards,
Mike
"me too" from our logs. Since these are concurrency-related errors, looks to me as if they're under attack and limit the number of inbound connections. Will probably clear itself up.
Cheers, Markus
On Wed, Aug 28, 2013 at 9:35 AM, Michael Richter MRichter@sasag.ch wrote:
mrichter@CL-LINUX-3OG-MR:~$ telnet mxzhh.bluewin.ch 25 Trying 195.186.227.50... Connected to mxzhh.bluewin.ch. Escape character is '^]'. 421 4.4.5 Service unavailable, concurrency limit reached. Connection closed by foreign host.
Trying 195.186.227.50... telnet: connect to address 195.186.227.50: Connection refused telnet: Unable to connect to remote host
This with all 3 MX:
bluewin.ch. 88 IN MX 10 mxbw.bluewin.ch. bluewin.ch. 88 IN MX 42 mxzhb.bluewin.ch. bluewin.ch. 88 IN MX 42 mxzhh.bluewin.ch.
I just wanted to verify this and the very first time it worked:
# telnet mxzhh.bluewin.ch 25 Trying 195.186.227.50... Connected to mxzhh.bluewin.ch. Escape character is '^]'. 220 zhhdzmsp-mxin28.bluewin.ch ESMTP Service (Swisscom Schweiz AG) ready
But right after I got the same error as you:
# telnet mxzhh.bluewin.ch 25 Trying 195.186.227.50... Connected to mxzhh.bluewin.ch. Escape character is '^]'. 421 4.4.5 Service unavailable, concurrency limit reached. Connection closed by foreign host.
But then again...
# telnet mxbw.bluewin.ch 25 Trying 195.186.99.50... Connected to mxbw.bluewin.ch. Escape character is '^]'. 220 zhbdzmsp-mxin15.bluewin.ch ESMTP Service (Swisscom Schweiz AG) ready
# telnet mxbw.bluewin.ch 25 Trying 195.186.99.50... telnet: Unable to connect to remote host: Connection refused
# telnet mxzhb.bluewin.ch 25 Trying 195.186.99.50... Connected to mxzhb.bluewin.ch. Escape character is '^]'. 220 zhbdzmsp-mxin19.bluewin.ch ESMTP Service (Swisscom Schweiz AG) ready
Seem to be very "random" problems: - 421 4.4.5 Service unavailable, concurrency limit reached. - Unable to connect to remote host: Connection refused - Sometimes connection works fine
On 28 Aug 2013, Michael Richter wrote:
Trying 195.186.227.50... Connected to mxzhh.bluewin.ch. Escape character is '^]'. 421 4.4.5 Service unavailable, concurrency limit reached.
We see the mail queues growing with undeliverable mails for bluewin.ch.
The same also happened on monday before Swisscom was unreachable. This reminds me of 2011 when they were attacked.
Regards
Oliver
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On 08/28/13 11:02, Oliver Hitz wrote:
On 28 Aug 2013, Michael Richter wrote:
Trying 195.186.227.50... Connected to mxzhh.bluewin.ch. Escape character is '^]'. 421 4.4.5 Service unavailable, concurrency limit reached.
We see the mail queues growing with undeliverable mails for bluewin.ch.
The same also happened on monday before Swisscom was unreachable. This reminds me of 2011 when they were attacked.
There was an attack and maybe it has amplified this issue but so far the root cause of the problem was a strange behavior of the bluewin MX load balancer (LB).
For unknown reasons, LB probes for MX server have failed although each MX server was running fine.
The LB started removing "failed" MX server from MXIN pool for several minutes. The pool got smaller and smaller. The load on the remaining pool was increasing until the concurrency limit was reached.
This issue was resolved at moon (GMT+2). An investigation is underway to find out how this happened.
Regards, Tom
-
Claudio Kuenzler -
Markus Wild -
Michael Richter -
Mike Kellenberger -
Oliver Hitz -
Thomas Vogt