how many SMTP/Submit clients use CHUNKING and BINARYMIME

Are there any Mail User Agents that use BINARYMIME (and CHUNKING, of
course) to submit messages, if the submission server supports
BINARYMIME+CHUNKING? Or do all the MUAs just encode their attachments
using base64/quoted-printable and not bother checking to see if they
need to?

        Tony