How to Configure DKIM for Sendmail on Ubuntu

Learn how to configure DKIM for Sendmail on Ubuntu. Our Sendmail Support team is here to help you with your questions and concerns.

How to Configure DKIM for Sendmail on Ubuntu: A Beginner’s Tutorial

DKIM is short for DomainKeys Identified Mail. It is a key email authentication method that makes sure our emails are from our domain and haven’t been tampered with.

In fact, it is a key defense against email spoofing. It is used by major email providers to fight spam and phishing. Our experts have put together this guide to help you set up DKIM for your domain.

1. First, install OpenDKIM and the needed tools on the server. Open a terminal and run:

   sudo apt-get install opendkim opendkim-tools
2. Next, create a directory to store the domain’s DKIM keys. Replace `DOMAIN.COM` with the actual domain name:

   sudo mkdir -p /etc/opendkim/keys/DOMAIN.COM
3. Then, generate the DKIM keys as seen here:

   sudo opendkim-genkey -D /etc/opendkim/keys/DOMAIN.COM -d DOMAIN.COM -s default

   So, this will create two files in the specified directory: `default.private` (the private key) and `default.txt` (the public key).
4. Next, make sure the permissions are correctly set for the key files:

   sudo chown -R opendkim:opendkim /etc/opendkim/keys/DOMAIN.COM
   
   sudo chmod 640 /etc/opendkim/keys/DOMAIN.COM/default.private
   
   sudo chmod 644 /etc/opendkim/keys/DOMAIN.COM/default.txt
   
   
5. Now, it is time to edit the OpenDKIM configuration file (/etc/opendkim.conf) and add these lines. Also. replacing `DOMAIN.COM` with your actual domain:

   
   
   Domain            DOMAIN.COM
   
   KeyFile            /etc/opendkim/keys/DOMAIN.COM/default.private
   
   Selector           default
   
   
6. Then, edit the OpenDKIM default settings and add this line to specify the socket:

   SOCKET="inet:8891@localhost"
7. Now, edit the Sendmail configuration file and add the following line to the configuration:

   INPUT_MAIL_FILTER(`opendkim', `S=inet:8891@localhost')
8. Also, rebuild the Sendmail configuration and restart the services:

   sudo sendmailconfig
   
   sudo service sendmail restart
   
   sudo service opendkim start
   
   

After following these steps, our Sendmail should be configured to sign outgoing emails with DKIM. This will make sure our emails are authenticated and secure.

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Conclusion

In brief, our Support Experts demonstrated how to configure DKIM for Sendmail on Ubuntu.