diff --git a/clients/mail500/sendmail.cf b/clients/mail500/sendmail.cf
index b7ec14d1ce..477162f10b 100644
--- a/clients/mail500/sendmail.cf
+++ b/clients/mail500/sendmail.cf
@@ -1,3 +1,8 @@
+#
+# It's recommended use Sendmail's m4 configuration system to avoid
+# mucking directly with .cf files
+#
+
 # Mostly rfc1123 compliant sendmail.cf
 #
 # Mail sendmail-admins-request@itd.umich.edu to join