[exim] Accept all mail for examination

I am working on some php and asp code which generated emails. I would like to
configure exim so that it accepts all mail on the SMTP port and then make the
mail available so that I can examine it to ensure my asp/php code is correct.

I have exim configured by Debian as 'local delivery only; not on a network.'
Mail that is created by the php code generates an error (since it can not
foward mail on to the real host) and that is fine since it does put the mail in
/var/mail/www-data (the apache account).

I can get exim to accept mail from the adjacent machine if the user account
exists. However, if the user account does not exist, the mail is not accepted
and therefore I can not examine it to determine if it is correct.

How can I tell exim to accept all mail? I would be happy to have it dumped into
any file in /var/mail/.

Thanks.

-Eric