https://dkimcore.org/tools/keys.html

https://tools.socketlabs.com/dkim/generator

https://easyengine.io/tutorials/mail/dkim-postfix-ubuntu/

opendkim-genkey -t -s google -d tech2solve.com

https://easydmarc.com/blog/how-to-configure-dkim-opendkim-with-postfix/