Is there a way to broadcast a message to all the company Propspace users?

Yes. PropSpace would let you broadcast a message to all the users within the company.

Step 1. Click the sticky note from the upper right corner of the screen.

Step 2. Click the Notes Tab. Then type the desired message.

Step 3. Click the send as Broadcast Message. Everyone in the company with Propspace user account will be able to receive the message.