Chapter 8: E-mail Gateways, Filtering, and Redundancy

Overview

E-mail has become one of the most critical technology aspects of business today. It is fairly well understood in the IT community because it shares some characteristics of regular postal mail or " snail mail." An address is used to distinguish the appropriate recipient. The e-mail server or "postal system" uses a predefined process to determine where to send the e-mail. Once this has been determined, the routing architecture of the Internet is used to route the e-mail to the appropriate destination.

This chapter will provide information on the following:

• E-mail Background A brief explanation of the protocols used to transfer e-mail as well as various client access protocols.

• E-mail Abuse How attackers and spammers are abusing e-mail systems today.

• Message Transfer Agents (MTAs) The differences between MTAs (built-in, stand-alone, etc.) will be analyzed .

• Relay Security and Blocking Lists How blocking lists are used to help in the fight against spam. This includes open relays and open proxies that proxy SMTP. Additionally, URI RBLs are discussed as a means of blocking spam based on information within the e-mail message.

• MTA Filtering Using your MTA to filter viruses and spam. Various techniques and practices are discussed to minimize the amount of spam received as well as the risk of unknowingly sending spam from your organization's resources.

• MTA Encryption Explanations on how to use opportunistic TLS with SMTP, and so on.

• MTA Redundancy Best practices when creating a redundant MTA infrastructure to include mail exchanger (MX) redundancy, geographic redundancy, and system redundancy.

• Remote/Client Security How to secure remote e-mail clients such as POP3, IMAP, web access, and more.

• Public Notifications and Role Accounts How to configure your organization's e-mail infrastructure to comply with RFCs and to be good stewards of the Internet with public notification capabilities.