[Exim] drop emails in direcory?

Hi,

I want to setup exim so that emails to three accounts (not really existing
UNIX accounts, just aliases) would be dropped into a directory. Say, emails
going to user@domain would be dropped (not just copied, because there's no
mail spool for that user) into /usr/local/user_mail/. What does my
/etc/aliases have to look like to get this working?

Thanks,
IvanK.

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