[Exim] Setting RCPT TO during LMTP with Exim 4

I think this is an easy one. I just can't see the answer.

I receive email with addresses like <anyone@???> that I map
with a lookup to the account matt. I then open up an LMTP connection to
Cyrus to deliver the email to the matt mailbox. The only problem is I
can run deliver -l -- matt but Exim sends RCPT TO:<anyone@???>
which results in an error. I need Exim to send RCPT TO:<matt> and leave
the To: header as <anyone@???>.

Any suggestions on the simplest way to do this with Exim 4.10?

Matt
matt@???