message
message-id
mime-version
+mixed
model
multipart
multipart/mixed
octet-stream
organization
pgp
-pgp-encrypt
+pgp-encrypted
pgp-keys
+pgp-signature
pgp-signed
pkcs7-mime
+pkcs7-signature
plain
postscript
print
us-ascii
utf-8
video
-x-comment-to
x-convert
x-label
x-mutt-deleted
x-pgp-message
x-pkcs7-mime
+x-pkcs7-signature
xref
x-status
x-uuencode