Postfix/Any Email Server check for Open Relay

The first thing you need to remember is not to check from the same host/server itself. This is a silly mistake I made, the reason is that many mailservers and especially postfix are configured to allow relaying from the localhost/same host. If you do that you'll get a false positive.

*Make sure you test from another host/system than the mail server itself!

telnet yourmailserverhost.com 25


220 Courier (FreeBSD 6.0)

helo server.amil.com
250 mail.cm.com
mail from:
250 2.1.0 Ok
rcpt to:

You should get an error message like this now:

554 5.7.1 : Relay access denied

If you get this instead you have an open relay and have to fix your mailserver. It should only allow mail to other destinations IF the user has logged in successfully.


250 2.1.5 Ok


Tags:

postfix, email, server, relaythe, mailservers, configured, relaying, localhost, ll, telnet, yourmailserverhost, courier, freebsd, helo, amil, cm, jkd, jk, ok, rcpt, hotmail, dkdkd, relay, mailserver, destinations, user, logged, successfully,

Latest Articles

  • 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
  • ffmpeg how to concat and join two video clips
  • mencoder instead of ffmpeg to join or concatenate video files with different audio streams
  • Linux How To Stop Missing Drive from Halting Boot Process in fstab
  • How To Replace Audio Track of Video using ffmpeg
  • qemu-img convert formats vdi vmdk raw qcow2
  • Linux and Windows Dual Boot Crazy Time Issues
  • dynagen / dynamips 100% high CPU usage solution - how to set the idlepc value
  • How To Setup a Cisco CME (Cisco Manager Express) Virtual Router under Linux using dynamips and dynagen
  • Linux Mint Ubuntu Debian CentOS Dual Boot Install Issues
  • Linux Mint Ubuntu Debian Centos RHEL no sound solution
  • Linux Mint/Debian/Ubuntu/Centos Installer black grub screen and blank screen after trying to boot installer or main OS
  • Linux Mint Dual Boot Install Avoid Wiping our your Main C: drive /dev/sda MBR and EFI
  • QEMU-KVM soundhw deprecated how to enable sound in QEMU 4.x series
  • Virtualbox Error Cannot register the hard disk because a hard disk with UUID already exists solution