Category Archives: Mail

Urdu CBT Linux System Administration qmail 1/7

It explains how you can configure qmail SMTP server (written by Dan Bernstein), with all the bells and whistles, using steps outlined by the creator of website (now de-functional). The qmailrocks guide was somewhat in-sufficient in explaining how qmail actually works. It just spoon-feeds you the steps to do (copy/paste). I was learning qmail myself when I created these CBTs, so there are areas in this CBT which are weak. I don’t recommend this CBT to be used to setup a production qmail server. It has only been uploaded for archiving reason. If you really want to learn qmail, the best sources are “Life with Qmail” and John Simpson’s “” .

Author: Muhammad Kamran Azeem

Published by:

Installing Nagios core on RHEL / CENTOS 5.x – RHEL / CentOS 6.x Fedora 15/16/17/18/19/20

What is Nagios

An enterprise-class monitoring and alerting solution that provides organizations with extended insight of their IT infrastructure before problems affect critical business processes.


We require following things for Installing Nagios:
These are Just Pre-requisites. We need them to other things work …

1. Apache and PhP (php is optional)
2. gcc, glib, glibc-common, gd and gd-devel

Continue reading

Published by:

Postfix Mail Delivery SMTP Troubleshooting

Articles CentOS Email How To How To's Linux Mail Mail Server Postfix SMTP Tips and Tricks troubleshooting

To avoid delay in emails, specially for gmail. Just find which MX is working by issuing below commands:

# dig mx

# telnet mx-IP/name 25

upon success, just see the name of first mx tried from /var/log/maillog

and add an entry in /etc/hosts file.

In my case, the entry is given below:
# vim /etc/hosts

:save and exit

now open postfix and add smtp_host_lookup directive under inet_protocols = all

# vim /etc/postfix/

inet_protocols = all
save and exit

now restart postfix

# service postfix restart

by default postfix host lookup is done via DNS, native mode uses nsswitch.conf settings and will check /etc/hosts first and then DNS if entry not found in /etc/hosts

Published by: