Deploy Exim as a Send-only Mail Server on Ubuntu 12.04

Many Linux server applications need to send email. Cron jobs use mail services to deliver reports on jobs that have run, web applications require mail support for user registration functions, and other applications may need to send alerts via SMTP. This guide will help you install and configure the lightweight Exim MTA (Mail Transfer Agent) on your Ubuntu 12.04 LTS (Precise Pangolin) Linode.

You’ll gain the ability to send mail from localhost through either a traditional “sendmail” style interface or via port 25 locally. As this guide is not intended to provide a full send/receive mail solution, please refer to our other email guides for ways to implement such configurations.

We assume that you’ve already followed the steps outlined in our getting started guide. If you are new to Linux server administration, you may be interested in our introduction to Linux concepts guide, beginner’s guide and administration basics guide. Make sure you’re logged into your Linode as “root” via SSH before proceeding.

Set the Hostname

Before you begin installing and configuring the components described in this guide, please make sure you’ve followed our instructions for setting your hostname. Issue the following commands to make sure it is set properly:

hostname
hostname -f

Install Required Packages

Make sure you have the “universe” repositories enabled. Your /etc/apt/sources.list file should resemble this:

File: /etc/apt/sources.list

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

## main & restricted repositories deb http://us.archive.ubuntu.com/ubuntu/ precise main restricted deb-src http://us.archive.ubuntu.com/ubuntu/ precise main restricted deb http://security.ubuntu.com/ubuntu precise-security main restricted deb-src http://security.ubuntu.com/ubuntu precise-security main restricted ## universe repositories deb http://us.archive.ubuntu.com/ubuntu/ precise universe deb-src http://us.archive.ubuntu.com/ubuntu/ precise universe deb http://us.archive.ubuntu.com/ubuntu/ precise-updates universe deb-src http://us.archive.ubuntu.com/ubuntu/ precise-updates universe deb http://security.ubuntu.com/ubuntu precise-security universe deb-src http://security.ubuntu.com/ubuntu precise-security universe

Issue the following commands to update your package repositories, upgrade your system, and install Exim:

apt-get update
apt-get upgrade
apt-get install exim4-daemon-light mailutils

Configure Exim for Local Mail Service

Now you’re ready to configure Exim for local mail service. Here’s how:

1. Enter the following command to start Exim configuration:

   dpkg-reconfigure exim4-config
   

2. You’ll be presented with a welcome screen, followed by a screen asking what type mail delivery you’d like to support. Select the option for internet site, and then select Ok to continue.

3. Enter your system’s FQDN (fully qualified domain name) in the mail name configuration screen.

4. Enter 127.0.0.1 ; ::1 when asked which IP address to listen on for SMTP connections.

5. Make sure you list your FQDN, hostname, and localhost entries when you’re asked which destinations mail should be accepted for.

6. Leave the relay domains and relay machines fields blank.

7. Select No when asked whether to keep DNS queries to a minimum.

8. You may select either mbox or Maildir when asked about the delivery method used for incoming mail. While many utilities use mbox format, Maildir format can make handling individual locally delivered mail messages easier, and is widely supporting by a range of applications.

9. Accept the default non-split option for your mail configuration file. Enter at least one external email address (choose one that you check frequently) in addition to root when asked to specify postmaster mail recipients.

Test Your Mail Configuration

Issue the following command to send a test email, substituting an external email address for someone@somedomain.com.

echo "This is a test." | mail -s Testing someone@somedomain.com

Congratulations! You’ve configured Exim to send email from your Linode.

More Information

You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.

• Exim Homepage
• Email Guides