diff --git a/src/agents/smtp/smtpd.c b/src/agents/smtp/smtpd.c
index c69da9f..98c9efe 100644
--- a/src/agents/smtp/smtpd.c
+++ b/src/agents/smtp/smtpd.c
@@ -1796,7 +1796,7 @@ DeliverSMTPMessage (ConnectionStruct * Client, unsigned char *Sender,
             }
         }
         else if (Recips[0].Flags & DSN_HEADER) {
-            if (ConnWrite(Client->remotesmtp.conn, "RET=HDRS", 9) < 1) {
+            if (ConnWrite(Client->remotesmtp.conn, " RET=HDRS", 9) < 1) {
                 DELIVER_ERROR (DELIVER_TRY_LATER);
             }
         }