NEWS: document S/MIME support

NEWS

@@ -9,6 +9,20 @@ Xapian 1.3 support
   Notmuch should now build (and the test suite should pass) on recent
   releases of Xapian 1.3.x. It has been tested with Xapian 1.3.5.
 
+Limited support for S/MIME messages
+
+  Signature verification is supported, but not decryption. S/MIME
+  signature creation and S/MIME encryption are supported via built-in
+  support in Emacs. S/MIME support is not extensively tested at this
+  time.
+
+Command Line Interface
+----------------------
+
+`notmuch show` now supports verifying S/MIME signatures
+
+  This support relies on an appropriately configured `gpgsm`.
+
 Build System
 ------------
 
@@ -59,6 +73,11 @@ longer generate empty buffers
   (or, in some cases, displaying an empty buffer and throwing an
   error). This also affects re-display of the current thread.
 
+Handle S/MIME signatures in emacs
+
+  The emacs interface is now capable making and verifying S/MIME
+  signatures.
+
 `notmuch-message-address-insinuate` is now a no-op
 
   This reduces the amount of interference with non-notmuch uses of