ssh remote and local port forwarding

http://www.debianadmin.com/howto-use-ssh-local-and-remote-port-forwarding.html

Sender and receipient map for postfix for backing up sending and receiving emails

http://www.linuxquestions.org/questions/linux-software-2/postfix-features-on-fc3-323593/

Linux - Useful Commands

monitor ssh on remote machine:
watch nmap -sT -p 22