SquidGuard is a URL redirector used to use blacklists with the proxysoftware Squid. There are two big advantages to squidguard: it is fast and it is free.
Email is a program for the Unix environment that sends messages. You may think that this has already been done, and it has, but not with the quality and enhancements that email has! Have you ever wanted to send email from the command line using your SMTP server instead of sendmail? Have you ever wanted to send email without entering a confusing menu application and you only wanted to push a few command line options to route your email to the SMTP server of your choice? Did you want to encrypt that email with gpg before it was sent but wanted the email client to do it for you? If you answered yes to all of these questions, then email is for you. You can now send email via the command line to remote SMTP servers. You can have it encrypted to the recipient of your choice. This and many other possibilities are easily implemented with email.
wget http://www.cleancode.org/downloads/email/email-3.1.3.tar.gz
tar zxf email-3.1.3.tar.gz
cd email-3.1.3
./configure
make
make install