Exim rewriting addresses

[mdevin@ozemail.com.au]

I am having some difficulty understanding how the last section of /etc/exim.conf
rewrites addresses.
Here is the part of the config file in question:
*@localhost     ${lookup{$1}lsearch{/etc/email-addresses}\
                                                {$value}fail} Ffrsw
Here is what I have in /etc/email-addresses:
algemon: mdevin@ozemail.com.au

Now when I send mail from mutt as user algemon it seems to rewrite the addresses
OK.  If I send mail from Netscape I still have the sender: algemon in the header
but at least the From: header is correct.
But if I send mail from the command line with mailx like:
cat file.txt | mailx -s "Subject" algemon@localhost then I still see
headers like:

To: algemon@localhost
Subject: Subject
Message-ID: <E14uZbh-0001Xr-00@debian>
From: "algemon,,," <mdevin@ozemail.com.au>
Date: Tue, 01 May 2001 22:50:21 +1000

How do I set it up so that the From: field is rewritten to
"mdevin@ozemail.com.au"
when mailing from mailx?
And how do I set it up so that the Sender: field when mailing from Netscape is
"mdevin@ozemail.com.au
and nothing else?

Any ideas where the rewriting rule in exim.conf is wrong?

thanks.

Mark.