I have a Linux server Red Hat 5 Enterprise
IP 10.100.100.117/24
We don't have direct access to Internet
We are accessing internet via a proxy server
IP 10.100.100.172/24
Port 3128
I need to send mail from command prompt but I am unable to do so using
mail -s "Subject" <email_address>
I did export http_proxy=http://10.100.100.172:3128/
I have stop iptables also
I installed packages
sendmail-8.13.8-2.el5.i386.rpm sendmail-devel-8.13.8-2.el5.i386.rpm
sendmail-cf-8.13.8-2.el5.i386.rpm sendmail-doc-8.13.8-2.el5.i386.rpm

but I am unable to send mail via shell prompt plz guide me which steps i need to follow.

Is this http proxy server also set up for smtp (email protocol)? If not, you may not be able to do what you are trying, especially if there is a firewall on the proxy server blocking port 25 outgoing.