FC3 and new QMail install - sends ok, can't receive
 

Warning - might be a newbie gotcha.
I have an FC3 install with Webmin. It has QMail installed. I added a user and through webmin can see a panel to manager user mailboxes. I went to the new users mailbox and can see it, it allows sending mail and presumably reading because its headed "This user has no messages in...". If I choose "Compose mail" I get a panel with all the usual from: to: etc entries and mail I send goes out fine. The problem is currently all mail sent to that user bounces with the message "user@mydomain.com: sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1). Have I missed something on the qmail side or my email client please? Thanks

fist check email client software to use smtp auth while sending emails.
http://www.qmailrocks.org/clientconfig.htm

if you have still troubles, u may want to reinstall qmail by following the guide at http://www.qmailrocks.org

good luck.

Assuming that your qmail home is in /var/qmail, you need to edit the /var/qmail/control/rcpthosts and make sure the host you are sending to is in there.