What is the role of the Edge Transport server in a hybrid Exchange deployment?

In a hybrid Exchange deployment, the Edge Transport server plays a crucial role in routing mail between the on-premises Exchange environment and the Exchange Online service in the cloud. Its primary function is to serve as a secure bridge for email flow, ensuring that messages can be sent and received between the various mail systems efficiently.

The Edge Transport server operates at the perimeter of the organization's network, which provides an additional layer of security by filtering emails and performing anti-spam and anti-malware scans before messages reach the Exchange servers. By acting as a gateway, it helps manage mail traffic and maintains a clear boundary between the internal and external email environments.

In this hybrid setup, the Edge Transport server is vital for maintaining seamless connectivity between the local and cloud-based infrastructures, facilitating hybrid mail routing and ensuring that users in both environments can communicate effectively. This is what makes the choice regarding routing mail between on-premises and cloud environments the correct answer in this context.