Postfix or Exim for Controlling Headers

[mdevin <mdevin@ozemail.com.au>]

Which of Postfix or Exim is easier to customise?

Basically, I started looking into this when I noticed that headers from
my emails contain local usernames.  I have setup address rewriting in
Exim (currently) and tried with Postfix also.

Currently in exim.conf I have this rule for rewriting addresses:
*@localhost     ${lookup{$1}lsearch{/etc/email-addresses}\
                                                {$value}fail} Ffrsw
This rewrites the envelope From field, as well as the From, Reply-To,
and Sender headers.
And the "w" flag makes it rewrite the whole address not just the working
part.

I have this in /etc/email-addresses:
algemon: mdevin@ozemail.com.au

But still, if I send mail with mailx from the command line like:
cat file.txt | mailx -s "Subject" mdevin@ozemail.com.au
I get headers like this:
Subject: Subject
Message-ID: <E14w0yg-0000Ye-00@beast.home.net>
From: "algemon,,," <mdevin@ozemail.com.au>

How do I stop the from field containing the login name?  I want it to
just be mdevin@ozemail.com.au.  Would it be easier to do this with
Postfix or Exim?

Thanks

Mark.