Exim rewrite local_part lookup outgoing

[Gary Stainburn]

Hi folks.

I'm looking at rewrite rules in Exim. I'm looking at the Exim docs and the two 
things I'm trying to do are the two most common rewrites.

1) I'm successfully rewriting *@groucho.ringways.co.uk as @ringways.co.uk
(The Marx brothers are my four servers). The rule is:

^(.*)@groucho.ringways.co.uk $1 at ringways.co.uk fFrs

2) The bit I can't get working is converting the local user name to the alias, 
i.e. converting gstainb to gary.stainburn. If possible I'd like to use the 
aliases file as it's already set up and has the usual syntax of

gary.stainburn:	gstainb

Can anyone please give me the rule I need for this. If I need a seperate 
mirror file of the aliases I will do.

Gary