X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/a93dbf44ca97cc5e404ec6c889afd0a5f41c368a..0e83c1487c22c96953f57e103d0fefabb15abe77:/doc/doc-txt/experimental-spec.txt

diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt
index d51169073..5c8231123 100644
--- a/doc/doc-txt/experimental-spec.txt
+++ b/doc/doc-txt/experimental-spec.txt
@@ -808,9 +808,15 @@ Expanded as a whole; if unset, empty or forced-failure then no signing is done.
 If it is set, all three elements must be non-empty.
 
 The fourth element is optional, and if present consists of a comma-separated list
-of options.  The only option implemented so far is
-  timestamps    Add a t= tag to the generated AMS and AS headers, with the
-                current time.
+of options.  The options implemented are
+
+  timestamps    	Add a t= tag to the generated AMS and AS headers, with the
+                	current time.
+  expire[=<val>]	Add an x= tag to the generated AMS header, with an expiry time.
+			If the value <val> is an plain number it is used unchanged.
+			If it starts with a '+' then the following number is added
+                	to the current time, as an offset in seconds.
+			If a value is not given it defaults to a one month offset.
 
 [As of writing, gmail insist that a t= tag on the AS is mandatory]