Tricky (to me) mail splitting

[Kirk Strauser <kirk@strauser.com>]

I am using Emacs 21.1.1 (Debian/Woody), Gnus version 5.8.8, and BBDB version
2.32.

I currently split mail with BBDB and group splitting:

(setq
   nnmail-split-methods        'bbdb/gnus-split-method
   bbdb/gnus-split-nomatch-function 'gnus-group-split
)

All was good and happy in my world until this morning.  I decided to
implement an idea I read a while back on Slashdot where I create a unique
email address for every person or company I correspond with (I host my own
mail server so adding new virtual users is no problem).

The new form of address I want to use is kirk-xxxxx@strauser, where xxxxx is
a random integer.  Now, the part that's tricking me is that I want all of
those new email address to come into their own group, with bonus points if
the groups are auto-generated.  For example, mail to kirk-12345@strauser.com
should land in mail.filtered.12345 .  FWIW, I'll be using an nnvirtual group
matching (nnvirtual "nnml:mail\\.filtered\\..*") to collect all of the
pre-split mail into one group for convenient reading, but still leave the
messages in their individual groups to easily identify the sender.

My question, then, is where should I define the split rules for all of these
new groups?  I'd really prefer not to have to manually create each one and
set its group parameters (for the gnus-group-split method).

-- 
Kirk Strauser