The inline_smtp Perl script was created to allow filtering of incoming mail on a separate server that houses the mailspools without running a full-blown MTA. While it's possible to configure another MTA, e.g. postfix, to relay all mail to a smart host and do filtering through postfix, the queue can get behind easily, and on a busy host thousands of messages can get queued in a few hours causing delays in delivery from a few minutes to several hours. By filtering while redirecting, mail arrives without any delays, and can be filtered by a seperate host adding headers or content reducing the load on the final mail host.
Install-Sendmail will configure Sendmail and Fetchmail on your machine. This Perl script can be used to setup a mail server for a simple network or it can configure email on a dial up machine. All you need to know is your email address, login name and password and optionally, the IP addresses of your network.
Spammilt is a sendmail-milter which scans email headers for blacklisted relaying servers and locally predefined blacklisted domains/words. By default, when spammilt detects spam, it adds a warning to the header and the subject. It's also possible to reject such emails without bothering the recipient.