I have a dedicated server with several sub-domains. I named the master domain merlo.webhosting.com. It is not a registered domain name, and I don't use the IP it's registered at yet. One of my sub-domains is rmerlo.com. When I send mail from the sub-domain, email headers have this;

Return-path: <nobody@merlo.webhosting.com>
Received: from nobody by merlo.webhosting.com ...

My emails are being rejected from many of the recipients.

How can I set up my email to have a Return-path to me@rmerlo.com as well as the Received header?

Thanks in advanvce.