OT: Sorting by references using Sieve

[Tassilo Horn]

Hi Gnus users,

I use Gnus for reading newsgroups and mail using the nnimap backend.  I
do mail filtering on the server side using Sieve scripts.  This works
very nice for filtering out SPAM and moving mailing list messages to
special folders.

But there are some cases where manual filtering is required.  For
example I work on two projects A and B, both having a dedicated folder.
In both projects I communicate with John Doe, so I cannot filter by
address.  For each folder I use gcc-self (see Gnus group parameters) to
keep my own messages in the folder, too, so that I get a newsgroup style
thread view.

What I want is this: If I get a reply by John Doe, it should be filed
into the folder that contains the request I've sent, e.g. the folder
which contains the message with the Message-id found in John's
References header.

Is this doable with Sieve?  I had a quick look at the RFC, but couldn't
find something like that.

I know that I could use the gnus registry for that, but I'd prefer to
keep the filtering on the server side.  Anyway, it Sieve doesn't work
here, a short sample for a gnus registry/fancy splitting routine would
be appreciated, too.  One key point is that it mustn't interfer with the
server side filtering.  E.g. it should only look at articles which are
delivered to my INBOX, everything else was filtered by the server setup.

Thanks for any pointers,
Tassilo
-- 
My opinions may have changed, but not the fact that I am right.