Setting up DKIM with Dovecot and OpenDKIM on a MacOS Home Server
If you're running a home server with MacOS 12.7.6 and have installed Dovecot and Postfix, you might be wondering how to set up DomainKeys Identified Mail (DKIM) to improve the deliverability of your emails. This article will guide you through the process of setting up DKIM with Dovecot and OpenDKIM on your MacOS home server.
What is DKIM?
DKIM is a method used to verify the authenticity of an email message by adding a digital signature to the message's header. This signature can be verified by the recipient's email server, which helps to prevent email spoofing and phishing attacks. DKIM is widely used by email providers and is recommended by best practices for email deliverability.
Installing OpenDKIM
OpenDKIM is an open-source implementation of the DKIM specification. To install OpenDKIM on your MacOS home server, you can use the following command:
sudo brew install opendkim opendkim-milter
This will install both the OpenDKIM command-line tools and the OpenDKIM Milter, which is used to apply the DKIM signature to outgoing email messages.
Configuring OpenDKIM
Once OpenDKIM is installed, you'll need to configure it to work with Dovecot and Postfix. The first step is to create a new configuration file for OpenDKIM using the following command:
sudo nano /usr/local/etc/opendkim.conf
This will open the nano text editor with a blank file. You can then add the following configuration options:
Domain mydomain.com
KeyFile /usr/local/etc/opendkim/keys/mydomain.com/mail.private
Selector mail
Replace "mydomain.com" with your actual domain name, and make sure that the KeyFile path matches the location where you want to store your DKIM private key. The Selector value can be any string, but it's recommended to use "mail" as it's the default value used by many email providers.
Next, you'll need to generate a new DKIM private key using the following command:
sudo opendkim-genkey -r -d mydomain.com -s mail -o /usr/local/etc/opendkim/keys/mydomain.com/mail.private
This will generate a new DKIM private key and save it to the location specified in the KeyFile option in the OpenDKIM configuration file. You'll also need to create a corresponding DKIM public key and save it to a file called "mail.txt" in the same directory:
sudo opendkim-genkey -r -d mydomain.com -s mail -O hmac -o /usr/local/etc/opendkim/keys/mydomain.com/mail.txt
You can then add the contents of the "mail.txt" file to your domain's DNS records as a new TXT record. The record should look something like this:
mail._domainkey.mydomain.com. IN TXT "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCqK...Make sure to replace "mydomain.com" with your actual domain name and "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCqK..." with the actual contents of the "mail.txt" file.
Configuring Dovecot and Postfix
Once OpenDKIM is configured, you'll need to configure Dovecot and Postfix to use it. First, you'll need to add the following line to your Dovecot configuration file:
protocol lmtp {
mail_plugins = $mail_plugins imap_quota_compatible
Next, you'll need to configure Postfix to use OpenDKIM as a Milter. You can do this by adding the following line to your Postfix configuration file:
smtp\_milters = inet:localhost:8891
This will tell Postfix to use the OpenDKIM Milter running on localhost port 8891 to apply DKIM signatures to outgoing email messages.
Testing DKIM
Once DKIM is set up, you can test it by sending an email from your MacOS home server and checking the DKIM signature on the received message. You can use a tool like Mail-Tester to check the DKIM signature and other email deliverability factors.
- DKIM is a method used to verify the authenticity of email messages.
- OpenDKIM is an open-source implementation of the DKIM specification.
- To set up DKIM with Dovecot and OpenDKIM on a MacOS home server, you'll need to install OpenDKIM, configure it with your domain name and DKIM private key, generate a DKIM public key, add the public key to your domain's DNS records, and configure Dovecot and Postfix to use OpenDKIM as a Milter.
- You can test DKIM by sending an email from your MacOS home server and checking the DKIM signature on the received message using a tool like Mail-Tester.