DBOX is a free communication package for ISPs. It supports a large number of message formats such as RFC/UUCP, ZConnect, Janus/Janus2, Alphabox, and GSbox. It is designed for large installations and includes a WWW package with an email/HTML gateway, an HTML online shop, support for POP3/IMAP4, and personal homepages with HTTP/FTP upload.
PGP Pipe allows encrypting a data stream of arbitrary length with the IDEA chipher from PGP. It is fast and usefull for secure backups on tapes or across the network. To prevent that this program is considered "strong cryptography", the encryption routines are NOT included, so you have to get the PGP source to compile it.