[exim] rewriting to ignore case of local part

I have a rewrite for some user whowish to have their mail forwarded elsewhere as the following

*@* ${lookup{$1@$2}dbm{/etc/mail/eximvirtuser.db}{$value}fail}


and in my /etc/mail/eximvirtuser file i have entries like

fred@???: fred@???



which work fine, all his email goes off to the mailserver for somewhereelse.com
apart from any mail that is addressed to Fred@??? which stays on my system.

I tried adding another line

Fred@???: fred@???

but then the dbm file wont be built as it says there is a duplicate value.

Can someone help me with how to make my config ignore case for the local part in these situations?

Thanks


--
Confidentiality Notice: This email is confidential and may also be privileged. If you are not the intended recipient, please notify the sender IMMEDIATELY; you should not copy the email or use it for any purpose or disclose its contents to any other person. General Statement: Any statements made, or intentions expressed in this communication, may not necessarily reflect the view of Spider Networks, that no content herein may be held binding upon Spider Networks or any associate or any associated company unless confirmed by the issuance of a formal contractual document or purchase order.