Correspondence tag-set

Hello all,

I'm working with Electronic Enlightenment (http://www.e-enlightenment.com) working on eighteenth-century correspondence. EE has its own tagset for letter features and metadata, and I'm working on writing up a concordance between EE and TEI. I'm pretty unfamiliar with TEI at the moment, and I was wondering if anyone here might be able to steer me towards current developments in TEI tagsets for correspondence? I've been looking at correspSearch and CMIF for metadata, but I understand that correspondence features are still being standardised?

Thank you for your time.

Jack Orchard