[Exim] Webfrontend for forward and vacation?

Hi all,

I'd like my users who don't have shell-access to their mail-server to be
able to change their forward and vacation using a web-frontend.
My first thougt how to implement it would be to create a directory "forward/"
and I'd name the actual forward-files $localpart. I think a transport
checking for a forward-file and using it should be rather simple. A similar
setup should handle vacation-messages (C019).
A look at the FAQ and the config.samples convinced me that the exim-side is
rather simple and IMHO the frontend-side shouldn't be difficult either.

However, I think that such a web-frontend probably has been built already,
so I'd like to ask if someone can give me some hints (what to consider, etc.)
or could even give me a copy of their frontend using an open license.

If I have to write a web-frontend as described above myself, I'd publish it
under GPL and let you know.

--
CU,
Patrick.
"Never run on auto-pilot" - The Pragmatic Programmer