diff --git a/exim.conf.m4 b/exim.conf.m4
index 14b31a7..6a07148 100644
--- a/exim.conf.m4
+++ b/exim.conf.m4
@@ -5,6 +5,8 @@ define(`SMARTHOST', esyscmd(`echo -n $SMARTHOST'))dnl
 define(`SMARTHOST_USER', esyscmd(`echo -n $SMARTHOST_USER'))dnl
 define(`SMARTHOST_PASS', esyscmd(`echo -n $SMARTHOST_PASS'))dnl
 define(`RELAYNETS', esyscmd(`echo -n $RELAYNETS'))dnl
+define(`WHITELISTED_RECIPIENTS', esyscmd(`echo -n $WHITELISTED_RECIPIENTS'))dnl
+
 
 ifelse(SMARTHOST, `', `
 errprint(`Error: SMARTHOST not set')
@@ -59,8 +61,12 @@ begin acl
 acl_check_rcpt:
   accept
     hosts = RELAYNETS
+ifelse(SMARTHOST_USER, `', `', `
+  accept
+    domains = WHITELISTED_RECIPIENTS
+')
   deny
-    message = "Relaying denied"
+    message = "550 5.7.1 Relaying denied"
 
 ifelse(LOCALMAILNAME, `', `', `
 begin rewrite