Internal and external no-reply address.

Hi,

Kindly let me know the steps to identify the internal reply address to mails.

Eg: When I sent a mail and then tried to call back that mail. I got a reply from a user id that the message cannot call back at this time.

The id I got mail from is another user id which is not involved in the mail chain I tried to call back.

This is something like a postmaster or noreply address. Please let me know how do I find and configure this for internal and external mails.