I like the concept of predictive filing and using an extraction rule to feed into a search on a managed property. But it doesn't work for us in very many cases (probably less than 1%). This because the text extracted from the subject is only held in the address for the destination subsite, and hence no managed property. And we have over 15000 sites, and growing, so any SharePoint search can take time.

However, I already have that information in the Central Register we use for our Solution Profiles. So why not leverage that. Add extra parameters to the Extraction Rules config item to let me specify a column in the Central Register to search and another column to return for the suggested location. Maybe a third for operator type, eg StartsWith, Equals, Contains etc. Should be a lot faster as well.

cheers, Mike