Q. How do I allow receiving email from my own domain only? I am using Qmail mail server software under Fedora Core Linux.
A. You can change the behavior of the qmail system by modifying qmail's control files. This is essential as you do not want to become a source of open mail relay. By default qmail will not relay. However every persons need is different. You can force qmail to accept domain listed rcphosts file only.
Open file /var/qmail/control/rcpthosts
# vi /var/qmail/control/rcpthosts
And append your domain name to accept email. Here is my sample file from my own box:
Save the file. And restart qmail.
From the qmail man page, "Allowed RCPT domains. If rcpthosts is supplied, qmail-smtpd will reject any envelope recipient address with a domain not listed in rcpthosts. Exception: If the environment variable RELAYCLIENT is set, qmail-smtpd will ignore rcpthosts, and will append the value of RELAYCLIENT to each incoming recipient address. rcpthosts may include wildcards:
Envelope recipient addresses without @ signs are always allowed through."