The Final Frontier: Hacking Sendmail
Common wisdom on Linux has it that recompiling the Linux kernel is the meanest test of a system administrator's skills. While it's true that messing with kernel modules isn't trivial, there's a higher peak: hacking sendmail's configuration file. This tip shows you how to ruin your mail system with ease.
Sendmail, that crusty and ancient (but also bulletproof) mail program, relies on the /etc/sendmail.cf file. These days, that file is usually generated using a heap of macros, much as a piece of assembly code can be entirely coded in macros. You can, however, hack sendmail.cf by hand, as long as you bear all the consequences. In the end it's still a plain text file.
Standard wisdom says: "You can understand sendmail.cf if you spend enough time on it, but that time will probably not be well spent." Well, fair enough, but today's an idle day, so let's have a look anyway.
