[CentOS] help from community

Thu Apr 12 11:56:02 UTC 2012
Markus Falb <markus.falb at fasel.at>

On 12.4.2012 13:29, Prabhpal S. Mavi wrote:
> Dear All Greetings,
> 
> i am admin for ISP two years now, relay emails for more than 300 companies
> (CentOS/Postfix). Relaying more than 10,000 messages every hours
> successfully. no one has ever compliant for non delivery. but i cannot
> relay to this domain. The servers responsible for accepting messages are
> rejecting. i have given the whole log for experts to monitor.
> 
> it is something out of control, because it is not my problem. Our server
> has all record created (A,MX,PTR,SPF etc). i have three relay hosts fully
> functional. destination server is not accepting from any relay host.
> 
> can anyone try from his server and see if it is deliverable to
> ray at tata-nigeria.com
> 
> Thanks / Regards
> Prabhpal S. Mavi
> 
> Apr 12 11:06:00 titan postfix/qmgr[11860]: C3C142E4012:
> from=<****@digital-infotech.net>, size=1391, nrcpt=1 (queue active)
> Apr 12 11:06:02 titan postfix/smtp[12039]: C3C142E4012: host
> mx2.servershost.net[205.234.223.160] said: 450 4.1.7
> <****@digital-infotech.net>: Sender address rejected: unverified address:
> host mail.digital-infotech.net[41.211.25.193] said: 450 4.7.1 Client host
> rejected: cannot find your hostname, [205.234.223.198] (in reply to RCPT
> TO command) (in reply to RCPT TO command)
> Apr 12 11:06:03 titan postfix/smtp[12039]: C3C142E4012:
> to=<ray at tata-nigeria.com>, relay=mx3.servershost.net[66.225.214.101]:25,
> delay=1381, delays=1377/0.03/3.4/0.31, dsn=4.1.7, status=deferred (host
> mx3.servershost.net[66.225.214.101] said: 450 4.1.7
> <****@digital-infotech.net>: Sender address rejected: unverified address:
> host mail.digital-infotech.net[41.211.25.193] said: 450 4.7.1 Client host
> rejected: cannot find your hostname, [205.234.223.198] (in reply to RCPT
> TO command) (in reply to RCPT TO command))
> 
> Thanks / Regards
> Prabhpal S. Mavi

I think the destination server is trying a callback verification
http://en.wikipedia.org/wiki/Callback_verification
but that fails because your server is doing checks as described in
http://en.wikipedia.org/wiki/FCrDNS

$ host 205.234.223.198
198.223.234.205.in-addr.arpa domain name pointer mx4.servershost.net.
$ host mx4.servershost.net.
mx4.servershost.net has address 66.225.237.241
-- 
Kind Regards, Markus Falb

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