blacklisting a forger

[Dennis German]

I have received  many emails in the last hour which were undeliverable,
NOT sent by me.
It seems someone is forging usernames in my domain Real-World-Systems.com
as the "from:" and the "return-path:" .
Received-From-MTA: dns;triband-mum-59.184.51.13.mtnl.net.in


I have sent a message to ab...@mntl.net.in and helpd...@mtnl.net.in but 
no response.

How does an MTA get blacklisted??