MIME4CL
MIME4CL allows you to craft MIME compliant messages or to parse and handle them programmatically.

It depends on SCLF, NPG, and Gray streams (as implemented in SBCL/CMUCL, extending CL streams).

Homepage: http://wcp.sdf-eu.org/software/#mime4cl

Download: http://wcp.sdf-eu.org/software/mime4cl-20150207T211851.tbz

License: LGPL