If you'd like to prevent emails from being sent to specific people, you can add domains and email addresses to your blacklist. Each user has their own personal blacklist they can edit. There's also a team blacklist that only the account owner and managers and can edit.
To add multiple domains and email addresses, you can separate each one by adding a new line.
You can also blacklist contacts within a sequence by adjusting their status to blacklist. To remove the contact from being blacklisted within the sequence, you'll need to navigate to your safety settings and remove the domain.