[Exim] partial wildcard aliases

Hi there,

I'm trying to move from the qmail MTA to exim 4. The one feature I
haven't been able to figure out is one I really need: the ability for
wildcard aliases.

What I want is for all addresses of the form 'bg-*' to be sent to a
certain local user, and for 'tg-*' to be sent to another one.

I've seen answers on how to send *@some.domain to a given address, but
what I've tried for 'bg-*' doesn't work. Any tips for this?

Also, what IMAP servers are thought to work well with exim 4? Does
exim 4 work well with Maildir directories? Given the setup I have, I
think that sort of system would work better for me. If so, I think I
could keep using the same MTA.

Ben giddings