In Customer Control Panel> Mail> Change settings options called Use DomainKeys spam protection and Switch on greylisting spam protection are greyed out and cannot be enabled.
DomainKeys spam protection and Greylisting features are not implemented in Plesk Automation(PA). The reason why they are displayed in mail settings is a software issue #PPA-2362 that was fixed in PA 11.5 MU#11.
In order to fix the UI issue please install update 11 as described in the article.
You can also vote for these features to be implemented in PA on UserVoice portal.