Implementing a header firewall
When messages are passed from one server to another through SMTP, Exchange Edge, and Mailbox servers, add custom X-Header fields are added to 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 rule processing statuses. 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.
How to do it...
One of the most common uses of a header firewall is to remove the internal server infrastructure details from SMTP email 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...
