SquirrelMail Configuration Easy Steps (SquirrelMail + Sendmail + Apache On RedHat/CentOS/Fedora)

This tutorial explains how you can install and configure SquirrelMail on a RedHat/CentOS/Fedora based mail server which uses Sendmail and Apache.


Primary Mail Server:  linuxbox4 (
Domain Name:     abc.com
Trusted IP Pool:

Note:  Replace domain name and system name and IP according to your scenario.



1.  DNS is configured with proper MX record.
2.  All necessary packages/ softwares are installed.


Step 1:

Configure all service to start at boot time.

chkconfig sendmail on
chkconfig httpd  on
chkconfig dovecot on


Step 2:

Configure /etc/hosts file. In this scenario /etc/hosts file should look like this:    linuxbox4   www.abc.com 


Step 3:

Outgoing Mail Server Configuration (Sendmail):

Open /etc/mail/sendmail.mc file and change the following two lines.


DAEMON_OPTIONS(`Port=smtp,Addr=, Name=MTA')dnl 


dnl DAEMON_OPTIONS(`Port=smtp,Addr=, Name=MTA')dnl 
dnl FEATURE(`accept_unresolvable_domains')dnl 

Save and exit.

- First line here enables sendmail to receive incoming emails on all installed the NICs. Otherwise mail server would only be able to receive mails from it.

- Second line here tells sendmail, do not receive emails from mail servers whose PTR record is not configured in DNS server. This is a basic level SPAM control settings in sendmail.

Generate sendmail.cf file from sendmail.mc file.

m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf


Step 4:

Allow RELAY for trusts (organization's) IP addresses that you want to permit sending emails using this mail server. Open /etc/mail/access in this file we specify all those addresses that will be sending emails through this mail server. At the end of this file add the following line:

192.168.0 RELAY 

Save and exit and convert this text database into DB format by following command.

  makemap hash access.db < access 


Step 5:

Tell sendmail that it will be acting as a primary mail server for "abc.com" domain. We do this by adding domain name in /etc/mail/local-host-names. If this server is acting as a mail server for more then one domains then add names of all of the domains in this file on separate line. Open /etc/mail/local-host-names and add "abc.com" at the end of this file.

Note: A mail server can act as a primary mail server for more then one domains at the same time and as well as can act as a primary and secondary mail server for more than one domain at the same time.


Step 6:

All system users are mail users as well. Now create mail only users.

useradd -s /usr/sbin/smrsh mailuser1
useradd -s /usr/s2n/smrsh mailuser1

Also set their passwords:

passwd mailuser1
passwd mailuser2


Step 7:

Finally restart sendmail service.

  service sendmail restart
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