To delete personal information about attendees, follow these steps:
Go to your `Workspace`
Click on `Settings`
Click on `Setup`
Click on `Data & Privacy`
Uncheck the box `Keep data until further notice` under Data retention
Specify after how many days of inactivity a contact should be deleted by adjusting the number of days under Keep data for how many days after a person is last seen? This way, you keep your contact lists up to date and those who have not shown interest stop receiving invitations and mailings.
NOTE: The settings under Data retention is not made immediately, but the contacts are removed during the night.