Exim mail server configuration on Centos 7

What is Exim?

Exim is a mail transfer agent (MTA) used on Unix-like operating systems. Exim is free software distributed under the terms of the GNU General Public License, and it aims to be a general and flexible mailer with extensive facilities for checking incoming e-mail.

What is Dovecot?

Dovecot is an open source IMAP and POP3 email server for Linux/UNIX-like systems, written with security primarily in mind. Dovecot is an excellent choice for both small and large installations.



UPDATE THE SYSTEM

First off, ssh to your server and initiate a screen session using the command below:

## screen -U -S exim-dovecot
once you’re in a screen session, update your CentOS 7 VPS using yum as in:

## yum update


ENABLE EPEL REPOSITORY

Enable EPEL repository on the CentOS system using:

## yum install http://dl.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-2.noarch.rpm
if you get a 404 not found, go at http://dl.fedoraproject.org/pub/epel/7/x86_64/e/ and install the latest epel-release rpm package available.

check if EPEL has been enabled on your system using:

## yum repolist
once EPEL is enabled, install some useful tools using:

## yum install file perl-Mail-SPF.noarch openssl vim


GENERATE SSL CERTIFICATE

Since we are going to use SSL in Dovecot and Exim, we need to have an SSL certificate. You can purchase and use one of our GeoTrust SSL Certificates or you can create your own self-signed SSL certificate for mail.mydomain.com using the commands below:

## mkdir /root/SSL/mail.mydomain.com -p
## cd /root/SSL/mail.mydomain.com
## openssl req -nodes -x509 -newkey rsa:2048 -keyout mail.mydomain.com.key -out mail.mydomain.com.crt -days 365
Move the SSL certificate and key to /etc/ssl using:

## cp mail.mydomain.com.key mail.mydomain.com.crt /etc/ssl/


INSTALL AND CONFIGURE EXIM

Install exim on the CentOS 7 virtual server using yum:

## yum install exim
next, open /etc/exim/exim.conf with your favorite editor and configure exim as follows:

## cp /etc/exim/exim.conf{,.orig}
## vim /etc/exim/exim.conf

primary_hostname = mail.mydomain.com
domainlist local_domains = @ : mydomain.com

tls_advertise_hosts = *
tls_certificate = /etc/ssl/mail.mydomain.com.crt
tls_privatekey = /etc/ssl/mail.mydomain.com.key

auth_advertise_hosts = *
find the transport section and edit the following:

local_delivery:
  driver = appendfile
  directory = $home/Maildir
  maildir_format
  maildir_use_size_file
  delivery_date_add
  envelope_to_add
  return_path_add
scroll down the the authenticators section and add the following lines:

dovecot_login:
  driver = dovecot
  public_name = LOGIN
  server_socket = /var/run/dovecot/auth-client
  server_set_id = $auth1

dovecot_plain:
  driver = dovecot
  public_name = PLAIN
  server_socket = /var/run/dovecot/auth-client
  server_set_id = $auth1
Start the EXIM MTA and add it to system’s startup using systemctl

## systemctl start exim
## systemctl status exim
## systemctl enable exim


Exim Commands::
==============
Email Count
exim -bpc

Email queue details
exim -bp

Email header details
exim -Mvh ID

Email body details
exim -Mvb ID

Email log details
exim -Mvl ID

Email count with sender details
exim -bpr|grep "<"|awk {'print $4'}|cut -d"<" -f2|cut -d">" -f1|sort -n|uniq -c|sort -n

Count of emails sent from a sender
exiqgrep -f sendername|grep "<"|wc -l

Count of emails sent to a particular email
exiqgrep -f recipient|grep "<"|wc -l

Delete mails from a particular sender
exim -bpr| grep sendername| awk '{print $3}'|xargs exim -Mrm

List of frozen mails
exim -bp|grep frozen|wc -l

Delete frozen mails
exim -bp|grep frozen|awk {'print $3'}|xargs exim -Mrm

Summary of emails in the queue
exim -bp|exiqsumm

Display what exim is doing now
exiwhat


INSTALL AND CONFIGURE DOVECOT
===============================
Install Dovecot on the system using yum

## yum install dovecot
Once installed, configure SSL in Dovecot by editing the following:

## vim /etc/dovecot/conf.d/10-ssl.conf

ssl = yes
ssl_cert = </etc/ssl/mail.mydomain.com.crt
ssl_key = </etc/ssl/mail.mydomain.com.key
next, allow plaintext authentication in /etc/dovecot/conf.d/10-auth.conf:

## vim /etc/dovecot/conf.d/10-auth.conf

disable_plaintext_auth = no
auth_mechanisms = plain login
configure mailbox location and type in /etc/dovecot/conf.d/10-mail.conf:

## vim /etc/dovecot/conf.d/10-mail.conf

mail_location = maildir:~/Maildir
Set-up Dovecot so that is allows Exim to use its authentication system in /etc/dovecot/conf.d/10-master.conf

## vim /etc/dovecot/conf.d/10-master.conf

service auth {
...
    unix_listener auth-client {
        mode = 0660
        user = exim
    }
}
Start Dovecot and add it to system’s start-up using:

## systemctl start dovecot
## systemctl status dovecot
## systemctl enable dovecot


CREATE SYSTEM USER

## useradd -m test
## passwd test