exim pros?

Totally outside of IW but I have a migration issue, wondering if anyone is an exim expert. My guy went rogue…

Long story but I need to keep my existing exim4 email server up while we migrate to IW.

Can anyone help with a routing configuration script that will relay all mail to my new IW server except 1 email “thisuser@mydomain.com” ?

Which file would contain the script and what would it be?

02/19/2005  06:25 AM               514 00_exim4-config_header
04/16/2005  03:51 AM               648 100_exim4-config_domain_literal
06/23/2006  12:54 PM               556 150_exim4-config_hubbed_hosts
09/03/2014  03:20 AM             4,485 200_exim4-config_primary
10/13/2007  03:27 AM               607 300_exim4-config_real_local
11/05/2006  04:53 AM             1,594 400_exim4-config_system_aliases
02/19/2005  06:25 AM               878 500_exim4-config_hubuser
08/16/2006  04:31 AM             2,104 600_exim4-config_userforward
02/19/2005  06:25 AM               403 700_exim4-config_procmail
02/19/2005  06:25 AM               323 800_exim4-config_maildrop
11/29/2008  06:11 AM               907 850_exim4-config_lowuid
04/13/2013  01:13 PM               602 900_exim4-config_local_user
04/13/2013  01:13 PM               802 999_exim4-config_mysql_user
02/19/2005  06:25 AM               472 mmm_mail4root

Thank you!