When most people install a free software mail transport agent (MTA) they plumb for Postfix, Exim, qmail or Sendmail. They can be a little over the top for some smaller systems or systems where all you need is some kind of local MTA functionality. In these cases many people will install their favourite MTA anyway but there are more lightweight alternatives. Here I look at one of them: Smail.
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Smail is more than likely a package on your system. On a Debian system its just an apt-get install smail away. If you are running testing or unstable youll not find a package for it I assume thats because theres no later version that the stable one. In that case just download it from Debians website. Finally, Smail can operate in a number of modes, one of these uses UUCP to a smarthost: if you want to use it that way you need to ensure uucp is installed as well.