How is possible find and delete messages base on string - Saas Netbackup

Hi guys,

In deletion policy I don't see a filter for specifying regular string.  Do you have idea how is possible delete the messages where in body or in subject of the message is example "Welcome to our presentation" ?

I suppose to usage a tag. So, tag behavior is applied for DLP protection of items. Which behavior I should be select, if I want to delete messages ?

Thanks for an advice Petr