+ ``--decrypt=(true|auto|false)``
+
+ If ``true`` and the message is encrypted, try to decrypt the
+ message while indexing. If ``auto``, and notmuch already
+ knows about a session key for the message, it will try
+ decrypting using that session key but will not try to access
+ the user's secret keys. If decryption is successful, index
+ the cleartext itself. Either way, the message is always
+ stored to disk in its original form (ciphertext).
+
+ Be aware that the index is likely sufficient to reconstruct
+ the cleartext of the message itself, so please ensure that the
+ notmuch message index is adequately protected. DO NOT USE
+ ``--decrypt=true`` without considering the security of
+ your index.
+
+ See also ``index.decrypt`` in **notmuch-config(1)**.
+