In this chapter, we discussed how to secure your installation. There were several different topics covered, firstly, the configuration of Postfix to only accept e-mail from certain IP addresses, which is useful if all your users are office based. Next, the chapter covered using SASL to authenticate users who might connect from any IP address. Then, we looked at using TLS to encrypt the authentication between client and server. Finally, we looked at limiting clients which behave badly, using the anvil
daemon to limit clients that connect too often within a certain time period, and clients that open too many connections at one time.
The measures shown in this chapter will make your life as a postmaster easier, and also help to limit the amount of spam that your users endure, and if you had inadvertently configured an open relay, limit the amount of spam passed on to other Internet users too. For more details on limiting spam, move on to Chapter 8 that describes using the open source...