Mail Server Configuration on Linux

Linux can be configured as a local mail server. This has been tested on the standard Fedora core 7 Linux distro. Here Linux is configured for relaying mails only in the local domain (example.com).

Server side Configuration

Server: Fedora core 7

Installed packages:

Sendmail server

1.       sendmail  -8.14.1-4.2.fc7 & sendmail -cf -8.14.1-4.2.fc7 (packages)

Pop  server

2.       dovecot ( imap/pop3) server

dovecot-1.0.0.11.fc7 (package

Mail Client

3.        Evolution/Thunderbird (for Linux) standard package shipped with Red Hat/Fedora, outlook(for windows)

Or a web based client such as “squirrelmail” can be used for accessing mails using web browser.

squirrelmail-1.4.10a-1.fc7 (package)

Other packages required for web based access (squirrelmail only) of mails are: 

Apache

php

 All standard Linux versions are shipped with apache (httpd) server and php.

   

 Mail Server Configuration

 Firstly we will make a local domain(example.com) on the linux server so that we can create emails as username@example.com

We shall change the hostname of our Linux server to “mailserver” by using the following command

# hostname mailserver

Also edit the file /etc/sysconfig/network to change the HOSTNAME=mailserver.

# hostname

Would  show the changed hostname as “mailserver” ( For our Linux Mail server)

Domain creation

After this we need to create a local domain on Linux server. For this we will edit the /etc/hosts file and add below entry to it below the”127.0.0.1    localhost.localdomain      localhost” line.

192.168.10.221     mailserver.example.com      mailserver

Save the file and exit. Upon exiting type the following command and we should have our dns domain as example.com

# dnsdomainname

Would give output as

example.com

Hence we have created a local domain in Linux by the name of “ example.com”

After this add users on the Linux server using useradd command and give then passwords. This shell login & password will be used for accessing their e-mail accounts.

Next set an ip address for ur mail server,say(192.168.10.221) using following command

# /sbin/ifconfig   eth0   192.168.10.221

Sendmail configuration

Sendmail configuration is stored in /etc/mail  directory which contains the sendmail configuration fil as sendmail.cf. This file should not be directly edited using vi editor. Instead m4 macro is used to configure this file using the sendmail.mc  file as follows.

sendmail.mc   file is edited and the using m4 macro is used to create the sendmail.cf  file .

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

Edit the sendmail.mc  file using vi editor and find this line in it.

DAEMON_OPTIONS (`Port=smtp,Addr=127.0.0.1 , Name=MTA’ ) dnl

The above line tells mail server to listen on only loopback address(default setting for mailserver). Hence we should disable it to listen on all available interfaces( i.e it should listen on eth0 interface also for requests). Hence we will disable the above line by commenting it( placing “dnl” in the beginning)

dnl   DAEMON_OPTIONS (`Port=smtp,Addr=127.0.0.1 , Name=MTA’ ) dnl

Next find the  line with LOCAL_DOMAIN and change it to “example.com” in place of localhost.localdomain

Now run the above m4  command to create sendmail.cf  file .

After this restart the sendmail service.

Dovecot configuration

Dovecot  is an open source IMAP & POP3 server. The configuration file is located in /etc directory as dovecot.conf.

Edit the /etc/dovecot .conf file to make following changes in the lines below:

   Protocols = imap   imaps   pop3    pop3s

    listen = * , [::]

    disable_plaintext_auth = no

    ssl_disable = no

    mail_location = mbox:~/mail:INBOX=/var/mail/%u

    pop3_uidl_format = %08Xu%08Xv

    auth default {

                mechanisms =  plain

              }

Save , exit and restart the dovecot.

Note:  Dovecot automatically auto detects the user’s mailbox in most cases (mail_location path given above need not specified in all cases), but if Dovecot does not detect the mailbox for retrieving mails (see /var/log/maillog), then we have to specify the mail location path as above. Choose the mail location from the specified list of mail_location already in the dovecot.conf file.

Testing the Dovecot

#  telnet   192.168.10.221  pop3

Should  greet you with message “ Ok+ Dovecot ready”

Next login with user credentials as

# user  chandan

Should greet you with “+Ok “

# pass   chandan123 

Should greet you with “+Ok Logged in”