1 files changed, 1 insertions, 1 deletions

diff --git a/conf.d/040_transports.conf b/conf.d/040_transports.conf
index 6236616..4b75e39 100644
--- a/conf.d/040_transports.conf
+++ b/conf.d/040_transports.conf
@@ -24,7 +24,7 @@ remote_smtp:
 signed_smtp:
   driver             = smtp
   message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
-  dkim_domain        = $sender_address_domain
+  dkim_domain        = ${if def:authenticated_sender {$sender_address_domain}}
   dkim_selector      = $primary_hostname
   dkim_private_key   = DKIMDIR/$dkim_selector._domainkey.$dkim_domain.pem
   dkim_canon         = relaxed