Mail server

[Raj Har]

Hello experts,

I have configured my mail server (postfix) in intranet.
user can send mail from one user to another user via client s/w like
Thunderbird.
but user can send mail from telnet utility eg.
#telnet server ip  25

they can send mail from this system.

i wanna stop this utility and i wanna send some error message to client
.....

but my mail server should be run properly.

can i do this???

Thanks.