How to setup exim4 on Debian to use Gmail

Why bother configuring an SMTP mail server on your Linux desktop? Especially if you can send and receive all your emails within a web browser using your Gmail account, or with an email client such as Thunderbird.

My reasons are twofold:

• Some applications running on my desktop require SMTP to be set up.

  My desktop computer is used to stage a WordPress blog. For WordPress to send email, an SMTP server is required.

• To redirect local root emails.

  Some programs such as sudo send emails to alert the root user of critical security events. For instance, after 3 failed sudo login attempts. But unless these emails are forwarded to an Internet email account that I actually monitor, they are useless.

This post is about configuring exim4, the default mail server on Debian wheezy.

I assume that

• exim4 is already installed
• You have a valid Google Gmail account.

Follow the steps below to configure exim4 to send all outbound emails to a remote "smarthost", namely the Google Gmail SMTP server. The smarthost will take care of forwarding the emails to their final destinations.

1. Reconfigure exim4.

   By default, exim4 is set up for local email delivery only: no emails to remote domains. You can reconfigure the application using the dpkg-reconfigure command or edit directly the configuration file (/etc/exim4/update-exim4.conf.conf).

   $ sudo dpkg-reconfigure exim4-config
   

   
   
2. Specify exim4 parameters.

   When prompted by dpkg-reconfigure, enter the following values for the respective exim4 parameters.

   Parameters	Values
   General type of mail configuration	mail sent by smarthost; received via SMTP or fetchmail
   System mail name	localhost
   IP addresses to listen on for incoming SMTP connections	127.0.0.1 Note: external connections are refused.
   Other destinations for which mail is accepted	Leave empty.
   Machines to relay mail for	Leave empty.
   IP address or host name of the outgoing smarthost	smtp.gmail.com::587
   Hide local mail name in outgoing mail?	No
   Keep number of DNS-queries minimal (Dial-on-Demand)?	No
   Delivery method for local mail	mbox format in /var/mail/
   Split configuration into small files?	No

3. Provide the Gmail account and password.

   Append the following to /etc/exim4/passwd.client with the proper Gmail account and password:

   *.google.com:yourAccount@gmail.com:yourPassword
   

   This password file contains sensitive account information. You should verify its file permissions and ownership.

   $ ls -al /etc/exim4/passwd.client
   -rw-r----- 1 root Debian-exim 252 Mar 25 17:24 /etc/exim4/passwd.client
   

   If they are different from the above, use the following commands to set file permissions and ownership.

   $ sudo chown root:Debian-exim /etc/exim4/passwd.client
   $ sudo chmod 640 /etc/exim4/passwd.client
   

4. Reload exim4.

   $ sudo update-exim4.conf
   $ invoke-rc.d exim4 restart
   [ ok ] Stopping MTA for restart: exim4_listener.
   [ ok ] Restarting MTA: exim4.
   $ exim4 -qff
   

   The -qff parameter forces a delivery attempt for every message, whether frozen or not.

To test, send an email to yourself, and check your Inbox:

$ echo test only | mail -s 'Test Subject' myAddress@gmail.com

If you open the email, you will see that the From address in the email header is the Gmail account which you configured in /etc/exim4/passwd.client.

If you experience any issue with exim4, check its log file located at /var/log/exim4/mainlog.

Now that an SMTP server is set up, my next post explains how to redirect local root emails to an Internet email account of your choice.