Copy this and send this to your subcontractors from your work email:
We are using a platform called Buildr to collect closeout documents for [Insert Project Name]. This will allow us to streamline the collection of closeout documents as well as create an unparalleled and consistent closeout experience for [Insert Owner's Name] and other jobs in the future. Please click the link below to watch a short introduction of how we expect you to interact with the platform. Additionally, when we request documents from you, we will be using Buildr to send these emails. Please prepare your team to receive emails from buildrtech.com. Thank you for your cooperation and please feel free to email us should you have any questions about the process.
Buildr Introduction: https://help.buildrtech.com/en/articles/4694313-subcontractor-meet-buildr