install_opendkim.sh: Add an Authentication-Results: header field.

install_opendkim.sh

@@ -237,6 +237,12 @@ SignatureAlgorithm      rsa-sha256
 # because it is often the identity key used by reputation systems and thus
 # somewhat security sensitive.
 OversignHeaders         From
+
+# Add an "Authentication-Results:" header field even to unsigned messages
+# from domains with no "signs all" policy. The reported DKIM result will be
+# "none" in such cases. Normally unsigned mail from non-strict domains does
+# not cause the results header field to be added.
+AlwaysAddARHeader       yes
 EOF
    opendkim_needs_restart=true
    if [[ $? -eq 0 ]] ; then