Expand the file. Compile the source code. Add a user without a real shell account called Postfix to the system. Run a shell script to copy all the files to their proper locations. Turn off Sendmail.
Postfix also has considerable support for stopping spam.
Some users have reported a dramatic reduction in the quantity of spam they receive. Note that you have to make aggressive use of the anti-spam options to benefit. They're not configured by default. Thirty minutes after starting the process I was done. None of my users are aware that I made a major change to the server.