To send the mail to main server from any host machine IP address by using Postfix ?

sir,

In Linux, We use send mail from some specific client host IP address to main server by using postfix configuration.

Suppose Some unwanted users or other third persons hosts send the mail to main server then their IP address was blocked by using postfix configuration.

But,I want How to send the mail to main server from third persons host IP address or any other host machine IP address then it is possible, by using Postfix How to Configuration this...

there is any command for send mail to main server from any where other IP address by using postfix.......