var/log/mail.log:Jun 28 18:25:43 rt-dq postfix/smtpd[4931]: NOQUEUE: reject: RCPT from unknown[209.85.219.66]: 450 4.7.1 Client host rejected: cannot find your hostname, [209.85.219.66]; from=<tess...@gmail.com> to=< nti-ad...@quimica.ufpb.br> proto=ESMTP helo=<mail-oa0-f66.google.com>
Then, at this exactly mail server machine: # nslookup 209.85.219.66 Server: x.x.x.x Address: x.x.x.x#53 Non-authoritative answer: 66.219.85.209.in-addr.arpa name = mail-oa0-f66.google.com. Authoritative answers can be found from: 219.85.209.in-addr.arpa nameserver = ns1.google.com. 219.85.209.in-addr.arpa nameserver = ns3.google.com. 219.85.209.in-addr.arpa nameserver = ns2.google.com. 219.85.209.in-addr.arpa nameserver = ns4.google.com. ns1.google.com internet address = 216.239.32.10 So, postfix is complaining that "cannot find your hostname", but the reverse DNS is working just fine. Any clue!?