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:<jkd@jk.com>
250 2.1.0 Ok
rcpt to:<joe@hotmail.com>

You should get an error message like this now:

554 5.7.1 <dkdkd@hotmail.com>: 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

  • How to install gns3 on Linux Ubuntu Mint
  • How to convert audio for Asterisk .wav format
  • Using Cisco CME Router with Asterisk as a dial-peer
  • Cisco CME How To Configure SIP Trunk VOIP
  • Virtualbox host Only Network Error Failed to save host network interface parameter - Cannot change gateway IP of host only network
  • Cisco CME and C7200 Router Testing and Learning Environment on Ubuntu 20+ Setup Tutorial Guide
  • Abusive IP ranges blacklist
  • How to Install Any OS on a Physical Drive from Windows Using VMware Workstation (Linux, Windows, BSD)
  • CDN Cloudflare how to set and preserve the real IP of the client without modifying application code on Apache
  • CentOS 7 fix Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=container error was 14: curl#6 -
  • Ubuntu Debian How To Install Recommended Packages Automatically
  • How to set Linux Ubuntu Redhat Debian Command Line http https socks proxy for yum apt
  • How to resize a pdf without losing much quality in Linux Mint Ubuntu Debian Redhat Solution
  • qemu: could not load PC BIOS 'bios-256k.bin' solution
  • Proxmox How To Custom Partition During Install
  • Hyper-V Linux VM Boots to Black Screen, Storage, NIC Not Found Issues
  • Ubuntu Mint How to Fix Missing/Broken /dev and /dev/pts which causes terminal to immediately close exit and not work
  • How high can a Xeon CPU get?
  • bash fix PATH environment variable "command not found" solution
  • Ubuntu Linux Mint Debian Redhat Youtube Cannot Play HD or 4K videos, dropped frames or high CPU usage with Nvidia or AMD Driver