- Plesk admin access to your VPS
DomainKeys Identified Mail (DKIM) is a way to validate a domain name identity that is associated with an e-mail address via cryptographic authentication. This means that your clients can verify who is sending them an e-mail and protects you against imposters pretending to send from your e-mail address.
- Log into your Plesk Control Panel https://your-web-site-name:8443/
Websites & Domains
Tick "Use DKIM spam protection system to sign outgoing email messages"
DKIM has successfully been added.
You can test your DKIM at - https://www.mail-tester.com/spf-dkim-check