Thanks Raindl, Problem was fixed; but I don't want to open my spam filter server to spammers. Do you think that is a DNS configuration issue on our client's DNS? When I issue the following command on the spam filter server # nslookup client.ip.address Server: my.dns.serverip Address: my.dns.serverip#53
Non-authoritative answer: Client.ip.address.in-addr.arpa name = mail.clientdomain.com. Thanks for your help. -----Original Message----- From: owner-postfix-us...@postfix.org [mailto:owner-postfix-us...@postfix.org] On Behalf Of Reindl Harald Sent: Thursday, April 28, 2011 11:28 AM To: postfix-users@postfix.org Subject: Re: NOQUEUE: reject: RCPT from unknown[xxx.xxx.xxx]: 450 4.1.8 Am 28.04.2011 20:20, schrieb motty.cruz: > Hello, > > Looks like one of our clients are trying to email us but their emails > are getting rejected. I'm sorry I will not display customers ip > > Apr 28 11:11:12 host postfix/smtpd[48962]: warning: hostname > mail.tld.com does not resolve to address xxx.xxx.xxx Apr 28 11:11:12 > host postfix/smtpd[48962]: connect from unknown[xxx.xxx.xxx] Apr 28 > 11:11:12 host postfix/smtpd[48962]: NOQUEUE: reject: RCPT from > unknown[xxx.xxx.xxx]: 450 4.1.8 > <cli...@tld.com>: Sender address rejected: Domain not found; > from=<client.tld.com> to=<u...@mydomain.com> proto=ESMTP > helo=<mail.tld.com> 450 is a temporary error and the client will combe back or is not standard-conform > Sender address rejected: Domain not found your dns can not solve the sender-domain maybe a temporary dns-problem > reject_unknown_sender_domain says you want this behavior
