[exim] deliver mail bot smtp/pop

    I have a setup where I relay mail for a domain xyz.com. I would like to 
route mail that is going to xyz.com to its mailserver and also maintain a copy of
all this mail in a mailbox. More so I would like a scenario where If for some reason
I cannot reach the smtp server I reroute this mail to a mail box?. Has someone done
This before. Exim version is 4.43