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Chapter 9: Securing Internet Email
bound email, and it can be pointed to by our domain’s “MX” DNS record (i.e., it can
be advertised to the outside world as a mail server for email addressed to our
domain). Pretty good return on the investment of about 10 minutes of typing, no?
This may be enough to get Postfix working, but it probably isn’t
enough to secure it fully. Don’t stop reading yet!
Succinct though the seven-step method is, it may not be enough to get Postfix to do
what needs to be done for your network. Even if it is, it behooves you to dig a little
deeper: ignorance nearly always leads to bad security. Let’s take a closer look at what
we just did and then move on to some Postfix tricks.
Configuring Postfix
Like Sendmail, Postfix uses a .cf text file as its primary configuration file (logically
enough, it’s called main.cf). However, .cf files in Postfix use a simple
parame-
ter=$value
syntax. What’s more, these files are extremely well commented and use
highly descriptive variable names. If your email needs are simple enough, it’s possi-
ble for you to figure out much of what you need to know by editing main.cf and
reading its comments as you go.
You may wonder why, in our little seven-step procedure, so little information needed
to be entered in main.cf. The only thing we