diff --git a/files/Dockerfile b/files/Dockerfile
index 27bd58a..d272d59 100644
--- a/files/Dockerfile
+++ b/files/Dockerfile
@@ -15,8 +15,8 @@ FROM debian:buster-slim
 ARG DEBIAN_FRONTEND=noninteractive
 ENV LC_ALL C
 ENV SUBMISSION_ENABLE= \
-    SUBMISSION_RELAY_HOST=
-    SUBMISSION_RELAY_PORT=25
+    SUBMISSION_RELAY_HOST= \
+    SUBMISSION_RELAY_PORT=25 \
     SUBMISSION_RELAY_TRUSTED=yes \
     SUBMISSION_RELAY_USER= \
     SUBMISSION_RELAY_MASTER_USER= \