To implement this authentication mechanism, you can use a third party software called OpenDKIM. These are the steps you have to follow to deploy DKIM.
1. Install the necessary packages:
sudo apt-get install -y opendkim opendkim-tools
2. Create the folder for the DKIM keys:
sudo mkdir -vp /etc/opendkim/keys
3. Generate the DKIM keys:
sudo opendkim-genkey -s mail -d zentyal-domain.lan -D /etc/opendkim/keys
4. Configure the folder permissions:
chown -R opendkim:opendkim /etc/opendkim/ sudo chmod 0640 /etc/opendkim/keys/*.private
