Local mail not working -- QMAIL

[Bradley Miller]

For some reason or another, I can't get any outbound email from the server 
direct to work.  I can send mail from my Windows box, but if I try to do a:

>  mail me at somewhere.com

I get:

>su: /usr/bin/mail: No such file or directory

I can do a qmail-inject:

echo To: me at somewhere.com |/var/qmail/bin/qmail-inject

I'm not sure how this is supposed to work, but what is 
/var/qmail/bin/sendmail supposed to do? ? ?

HELP!