diff --git a/install/debian/11/exim/exim4.conf.template-RC b/install/debian/11/exim/exim4.conf.template-RC
index 605d848ab..36ba2a0d5 100644
--- a/install/debian/11/exim/exim4.conf.template-RC
+++ b/install/debian/11/exim/exim4.conf.template-RC
@@ -140,6 +140,11 @@ acl_check_rcpt:
 
   warn    set acl_m3    = no
   
+  warn    !authenticated = *
+          hosts          = !+relay_from_hosts
+          condition     = ${lookup{$local_part@$domain}lsearch{/etc/exim4/domains/$domain/aliases}{true}{false}}
+          set acl_m3    = yes
+
   deny    message       = Restricted characters in address
           domains       = +local_domains
           local_parts   = ^[.] : ^.*[@%!/|]