This is documentation for Plesk 12.5.
Go to documentation for the latest version, Plesk Obsidian.
Enabling DomainKeys Email Signing
To enable DomainKeys signing of outgoing email, go to Websites & Domains > Mail Settings, select the Use DomainKeys spam protection system to sign outgoing email messages checkbox and click OK.
Note: DomainKeys signing will function only for domains that use the Plesk DNS server.