- If true and the message is encrypted, try to decrypt the
- message while indexing. If decryption is successful, index
+ 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