Windows Server has a role that it can run in SMTP. Exchange and other services use this role to relay mail. There is a type of attack against a mail server that revolves around effectively performing a Denial of Service (DoS) against Exchange by sending massive quantities of mail to the server and forcing it to send Non Delivery Reports (NDRs) from the mail you’ve sent the server. This is known as an NDR Flood Attack. You can also leverage what’s known as a Directory Harvest Attack to get a server to respond to each possible combination of characters for addresses on domains running on an Exchange server. A Directory…