email server messsages rejected without reverse DNS DNS check failure Client host rejected: cannot find your reverse hostname Cannot resolve PTR record

Basically you should always be 100% sure that whatever IPyour mail server sends out with has reverse DNS/PTR records. Remember that unless you own your IPs then you won't be able to set your own reverse DNS. Even if you were to create a reverse PTR record on your DNS servers it will be ignored. Reverse DNS is queried to pre-assigned DNS servers of your ISP, so therefore you'll need to contact your ISP/Colo/Hosting provider to do a reverse DNS entry.

If you don't have reverse DNS you'll find many of your outgoing e-mails will be rejected and won't reach the recipient. You can usually check /var/log/maillog for lines like this:

  • DNS check failure
  • Client host rejected: cannot find your reverse hostname
  • Cannot resolve PTR record

Jan 31 01:04:21 mailserver postfix/smtp[20217]: 34CA233700CB: host mx.east.cox.net[68.1.17.3] refused to talk to me: 421 eastrmimpi03.cox.net IMP 12.55.42.121 DNS check failure - try again later - Refer to Error Codes section at http://postmaster.cox.net/confluence/display/postmaster/Error+Codes for more information.

Jan 31 01:04:22 mailserver postfix/smtp[20334]: 94FC33370078: to=, relay=mail.interbgc.com[217.9.224.121]:25, delay=221697, delays=221693/0.28/3.5/0.62, dsn=4.7.1, status=deferred (host mail.interbgc.com[217.9.224.121] said: 450 4.7.1 : Recipient address rejected: temporary failure: Please see http://spf.pobox.com/why.html?sender=postmaster%40mail.mailserver.com&ip=12.55.42.121&receiver=p1.interbgc.com (in reply to RCPT TO command))

Jan 31 01:04:26 mailserver postfix/smtp[20337]: 94F303370060: host mailin15.datevnet.de[193.27.50.115] said: 450 4.7.1 Client host rejected: cannot find your reverse hostname, [12.55.42.121] (in reply to RCPT TO command)

Jan 31 01:04:30 mailserver postfix/smtp[20332]: 95B0F33700DB: to=, relay=smtp-in2.nuvox.net[70.43.63.21]:25, delay=67120, delays=67108/0.27/12/0.05, dsn=4.7.1, status=deferred (host smtp-in2.nuvox.net[70.43.63.21] said: 450 4.7.1 Access temporarily denied. Cannot resolve PTR record for 12.55.42.121 SRC001 Contact postmaster@nuvox.net (in reply to MAIL FROM command))


Tags:

email, server, messsages, rejected, dns, hostname, resolve, ptr, recordbasically, ip, ips, servers, ignored, queried, assigned, isp, ll, colo, hosting, provider, entry, outgoing, mails, recipient, var, maillog, mailserver, postfix, smtp, ca, cb, mx, cox, eastrmimpi, imp, refer, codes, http, postmaster, confluence, display, fc, shanellmedsker, interbgc, relay, delays, dsn, deferred, shanellmr, spf, pobox, html, sender, receiver, reply, rcpt, mailin, datevnet, db, lamo, nuvox, temporarily, src,

Latest Articles

  • Aruba/HP/Dell IAP Wireless Controller Common Default Passwords
  • Debian, Mint Ubuntu how to remove package and associated config files
  • Linux Grub not booting the intended kernel solution in Debian, Mint, Ubuntu how to specify which kernel to boot by default
  • QEMU KVM Keyboard Problems Not Working Right Repeating Characters, Ctrl+C Copy and Paste not working right when using PS2 mouse in guests Solution
  • Linux how to compile binary with static sharedobjects embedded instead of dynamic to use on multi-distributions and avoid glibc compatiblity issues
  • /bin/sh: msgfmt: not found error solution on Linux Compilation Ubuntu Debian Mint Centos
  • Mikrotik RouterOS CHR/ISO Basic and Quick Setup Howto Guide
  • qemu 4 compilation options
  • CentOS 7 8 PXEBoot Netinstall Not Working Solution "Pane is dead "new value non-exisetnt xfs filesystem is not valid as a default fs type"
  • CentOS 6 EOL yum repo won't work Error: Cannot find a valid baseurl for repo: base Solution
  • CentOS 7 8 How To Disable SELinux
  • Wordpress How To Add Featured Image To Post in Hueman Theme
  • kdenlive full reset how to erase all config files
  • CentOS 7 8 yum error Trying other mirror. To address this issue please refer to the below wiki article
  • Microsoft Teams Linux - Calendar Doesn't Work Missed Meetings!
  • Scanner not working in Linux Ubuntu Fedora Mint Debian over the network? Use sane-airscan!
  • How To Boot, Install and Run Windows 2000 on QEMU-KVM
  • bash cannot execute permission denied
  • Huion and Wacom Tablets How To Install in Linux Mint / Ubuntu and make the stylus work properly
  • ffmpeg how to cut certain parts of video out