+ **index.decrypt**
+
+ **[STORED IN DATABASE]**
+
+ Policy for decrypting encrypted messages during indexing.
+ Must be one of: ``false``, ``auto``, ``nostash``, or
+ ``true``.
+
+ When indexing an encrypted e-mail message, if this variable is
+ set to ``true``, notmuch will try to decrypt the message and
+ index the cleartext, stashing a copy of any discovered session
+ keys for the message. If ``auto``, it will try to index the
+ cleartext if a stashed session key is already known for the message
+ (e.g. from a previous copy), but will not try to access your
+ secret keys. Use ``false`` to avoid decrypting even when a
+ stashed session key is already present.
+
+ ``nostash`` is the same as ``true`` except that it will not
+ stash newly-discovered session keys in the database.
+
+ From the command line (i.e. during **notmuch-new(1)**,
+ **notmuch-insert(1)**, or **notmuch-reindex(1)**), the user
+ can override the database's stored decryption policy with the
+ ``--decrypt=`` option.
+
+ Here is a table that summarizes the functionality of each of
+ these policies:
+
+ +------------------------+-------+------+---------+------+
+ | | false | auto | nostash | true |
+ +========================+=======+======+=========+======+
+ | Index cleartext using | | X | X | X |
+ | stashed session keys | | | | |
+ +------------------------+-------+------+---------+------+
+ | Index cleartext | | | X | X |
+ | using secret keys | | | | |
+ +------------------------+-------+------+---------+------+
+ | Stash session keys | | | | X |
+ +------------------------+-------+------+---------+------+
+ | Delete stashed session | X | | | |
+ | keys on reindex | | | | |
+ +------------------------+-------+------+---------+------+
+
+ Stashed session keys are kept in the database as properties
+ associated with the message. See ``session-key`` in
+ **notmuch-properties(7)** for more details about how they can
+ be useful.
+
+ Be aware that the notmuch index is likely sufficient (and a
+ stashed session key is certainly sufficient) to reconstruct
+ the cleartext of the message itself, so please ensure that the
+ notmuch message index is adequately protected. DO NOT USE
+ ``index.decrypt=true`` or ``index.decrypt=nostash`` without
+ considering the security of your index.
+
+ Default: ``auto``.
+