I've installed OpenDKIM to sign the outgoing emails sent from Postfix mail server following this guidelines:
- https://help.ubuntu.com/community/Postfix/DKIM
- https://www.exratione.com/2014/07/setting-up-spf-and-dkim-for-an-ubuntu-1404-mail-server/
After following them, I've checked the DKIM Key here and it successfully finds a DKIM key with the provided selector. But still the emails are not being signed properly with the private key. After troubleshooting I find that the OpenDKIM process is not running in the server.
Then I tried to run the process manually:
sudo service opendkim start
which results in following error:
Starting OpenDKIM: opendkim: /etc/opendkim.conf: /etc/postfix/dkim.key can be read or written by other users opendkim.
Before that I'd changed the permissions of dkim.key file to 755 and changed the ownership of the file to the user opendkim from the group opendkim:
sudo chmod 755 /etc/postfix/dkim.key
sudo chown opendkim:opendkim /etc/postfix/dkim.key
How can I run the process opendkim?