When messages are passed from one server to another through SMTP, Exchange edge and hub transport servers add custom X-Header fields into the message header. These headers can contain a variety of information such as mail server IP addresses, spam confidence levels (SCL), content filtering results, and rules processing status. Header firewalls are used to remove these custom X-Header fields so that unauthorized sources cannot obtain detailed information about your messaging environment. In this recipe, you'll learn how to use the Exchange Management Shell to implement a header firewall that prevents the disclosure of internal information sent to an external source.
One of the most common uses of a header firewall is to remove internal server infrastructure details from SMTP e-mail message headers destined for an external recipient. To do this on an edge transport server, you need to modify the permissions for the Internet send connector using...