How to get mail to local destinations delivered?

[Chris G]

I have a fairly default Fedora 7 installation, certainly the sendmail
is just as it was installed.

How do I get sendmail to deliver mail to local destinations?  The
system's hostname is home.isbd.net and it's connected to the Internet
via a router.  I have a CNAME set up at the hosting provider that
hosts isbd.net to point at the static address of my ADSL connection.

When I send mail from my system to a local address it gets the
hostname added, thus mail gets sent to root at home.isbd.net,
postmaster at home.isbd.net, chris at home.isbd.net, etc.  All of this
fails because sendmail attempts to connect to the SMTP port of
home.isbd.net, which isn't possible because my router's firewall
doesn't accept connections on port 25.

I don't want to open up port 25 and it seems a bit silly anyway to
send mail on such a long round trip.  Is there any way I can tell
sendmail that home.isbd.net is localhost (or 192.168.1.1)?  I have an
entry for home.isbd.net in my /etc/hosts file which is:-

    192.168.1.1     home    home.isbd.net

but obviously sendmail is doing a DNS lookup for home.isbd.net which
returns the 'external' IP address.

-- 
Chris Green