diff --git a/doc/utils.md b/doc/utils.md
index d62ad46..95846d9 100644
--- a/doc/utils.md
+++ b/doc/utils.md
@@ -203,6 +203,13 @@ predicate.
 
 A simple wrapper module to send emails from UNIX system.
 
+    (*mailto-override* [email])
+
+* ```email``` - email address string
+
+If this parameter is non-```#f```, all outgoing emails are actually
+sent to the address stored within.
+
     (send-mail body-lines [#:from from] [#:to to] [#:subject subject])
 
 * ```body-lines``` - lines of the email