how to send mail using command line

[Abhishek Dixit]

I installed Postfix on my system now I want to be able to send mails
via command line in my LAN.
How is that possible I typed a command mail on terminal and got following

The program 'mail' can be found in the following packages:
 * heirloom-mailx
 * mailutils
Try: apt-get install <selected package>

what exactly should I be doing to be able to send mail via command line.
-- 
Regards
Abhi