Can I use Leap Onboard to send posts to all our employees who are part of our company?

You can use Leap Onboard to communicate with not just candidates who are yet to join your company but even with your existing employees. Just add all your employees into Leap Onboard with a Joined status. You can then either use Campaigns by setting a date range for your posts; or use the Quick Message option to broadcast messages to candidates and employees of all departments.