On Mon, May 02, 2011 at 10:30:44PM +1100, Voytek Eymont wrote:
Hi guys, is that a genuine email from the list, I'm getting it rejected as it's missing reverse hostname:
May 2 21:21:41 postfix/smtpd[18033]: NOQUEUE: reject: RCPT from unknown[194.89.34.45]: 450 4.7.1 Client host rejected: cannot find your reverse hostname, [194.89.34.45]; from=<dovecot-bounces@dovecot.org> to=<voytek@sbt.net.au> proto=ESMTP helo=<mkentta.iki.fi>
# host mkentta.iki.fi mkentta.iki.fi has address 194.89.34.45 mkentta.iki.fi mail is handled by 10 mkentta.iki.fi. mkentta.iki.fi mail is handled by 100 smtp.menturagroup.com.
# host 194.89.34.45 Host 45.34.89.194.in-addr.arpa. not found: 3(NXDOMAIN)
We discussed this the other day under Timo's thread about dovecot.org. It seems that ns.ripe.net., one of the NS hosts for 89.194.in-addr.arpa., is not returning the PTR for 45.34.89.194.in-addr.arpa. AFAICS the other NS hosts seem to be working fine, but if your resolver was unlucky enough to hit ns.ripe.net., you have a host with no PTR.
It's like Russian roulette with rDNS. I suspect it might be a casualty of DNSSEC, but I get the same "noerror" response when querying with +dnssec and +nodnssec.
At this point those who use the normally safe and reasonable reject_unknown_reverse_client_hostname restriction should consider whitelisting mkentta.iki.fi[194.89.34.45] in the MTA.
And Timo needs to scream louder at the ISP. ;)
Offlist mail to this address is discarded unless
"/dev/rob0" or "not-spam" is in Subject: header