How can an Administrator change the IP of the email server for inbound email delivery?

The correct choice refers to the process where an Administrator can change the IP address of the email server that is responsible for handling inbound email delivery through the customization of Delivery Routes and Definitions within the Mimecast administration console.

In Mimecast, Delivery Routes are configured to determine how inbound emails are routed to the intended email server. By editing these settings, an Administrator can specify a new IP address to which emails should be directed. This allows for seamless transition and redirection of email traffic to the new server without the need for altering DNS configurations or physical network settings, thus providing a straightforward solution for managing email delivery routes.

While modifying network settings, updating DNS records, or contacting support may relate to email management, they do not directly address the need to change the specific IP address that Mimecast uses to deliver incoming emails. Changes to network settings typically pertain to local configurations, and DNS updates involve changes that can take time to propagate, which may not be instant solutions for re-routing email. Contacting Mimecast Support could be required in some complex scenarios, but for simply updating the delivery IP, editing the Delivery Route is the most efficient method.