Archive server OT

[Lyndon Labuschagne]

Hello All

This is largely off topic but I think the list users here are probably some of the most knowledgeable mail admins around

What I am looking at is a mail archive server(s) 
ideally it should be set as the MX server, 
all mail will arrive on the server be scanned etc as per the usual mailscanner way of doing things and then archive the mail in some way shape or form before delivering the mail to the client mail server.
it only has to keep the archive for a few days maybe a week or 2 at the most, 

Are there any products or projects that can do this sort of thing that any of you may have seen, 

I know there are some commercial hosted products for this sort of thing but ideally I would like to host this ourselves. 

Any info would be appreciated 


Thanks

Lyndon