report the specific properties used to the upstream notmuch project,
as a way of avoiding collisions in the property namespace.
+CONVENTIONS
+===========
+
+Any property with a key that starts with "index." will be removed (and
+possibly re-set) upon reindexing (see **notmuch-reindex(1)**).
+
+MESSAGE PROPERTIES
+==================
+
+The following properties are set by notmuch internally in the course
+of its normal activity.
+
+**index.decryption**
+ If a message contains encrypted content, and notmuch tries to
+ decrypt that content during indexing, it will add the property
+ ``index.decryption=success`` when the cleartext was successfully
+ indexed. If notmuch attempts to decrypt any part of a message
+ during indexing and that decryption attempt fails, it will add the
+ property ``index.decryption=failure`` to the message.
+
+ Note that it's possible for a single message to have both
+ ``index.decryption=success`` and ``index.decryption=failure``.
+ Consider an encrypted e-mail message that contains another
+ encrypted e-mail message as an attachment -- if the outer message
+ can be decrypted, but the attached part cannot, then both
+ properties will be set on the message as a whole.
+
+ If notmuch never tried to decrypt an encrypted message during
+ indexing (which is the default, see ``index.decrypt`` in
+ **notmuch-config(1)**), then this property will not be set on that
+ message.
+
+**session-key**
+
+ When **notmuch-show(1)** or **nomtuch-reply** encounters a message
+ with an encrypted part, if notmuch finds a ``session-key``
+ property associated with the message, it will try that stashed
+ session key for decryption.
+
+ If you do not want to use any stashed session keys that might be
+ present, you should pass those programs ``--decrypt=false``.
+
+ Using a stashed session key with "notmuch show" will speed up
+ rendering of long encrypted threads. It also allows the user to
+ destroy the secret part of any expired encryption-capable subkey
+ while still being able to read any retained messages for which
+ they have stashed the session key. This enables truly deletable
+ e-mail, since (once the session key and asymmetric subkey are both
+ destroyed) there are no keys left that can be used to decrypt any
+ copy of the original message previously stored by an adversary.
+
+ However, access to the stashed session key for an encrypted message
+ permits full byte-for-byte reconstruction of the cleartext
+ 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,
+ e.g. 9 means AES-256) followed by a colon, followed by a
+ hexadecimal representation of the algorithm-specific key. For
+ example, an AES-128 key might be stashed in a notmuch property as:
+ ``session-key=7:14B16AF65536C28AF209828DFE34C9E0``.
+
SEE ALSO
========
**notmuch(1)**,
+**notmuch-config(1)**,
**notmuch-dump(1)**,
**notmuch-insert(1)**,
**notmuch-new(1)**,
**notmuch-reindex(1)**,
+**notmuch-reply(1)**,
**notmuch-restore(1)**,
+**notmuch-show(1)**,
***notmuch-search-terms(7)**