message. This includes attachments, cryptographic signatures, and
other material that cannot be reconstructed from the index alone.
+ See ``index.decrypt`` in **notmuch-config(1)** for more
+ details about how to set notmuch's policy on when to store session
+ keys.
+
The session key should be in the ASCII text form produced by
GnuPG. For OpenPGP, that consists of a decimal representation of
the hash algorithm used (identified by number from RFC 4880,