Using my own domain when bounced emails are sent to the sender

When emails sent through my website bounce, it produces a message with the following:

This is the qmail-send program at I’m afraid I wasn’t able to deliver your message to the following addresses.

How do I modify this so that my domain shows instead of ? It would help the user know where this email really came from.

Thank you.

Hello? Still looking for some help.

There is nothing to change. The message you receive is for you, not the user. It is telling you, the program qmail-send running on so and so server failed to send email to certain addresses (I assumed they are listed), this is not a message your users see.