diff --git a/compose.smtp.yml b/compose.smtp.yml
index 60ac7d0..ebd2069 100644
--- a/compose.smtp.yml
+++ b/compose.smtp.yml
@@ -8,7 +8,7 @@ services:
       - GITEA_MAILER_ADDR
       - GITEA_MAILER_PORT
       - GITEA_MAILER_USER
-      - GITEA_MAILER_PROTOCOL
+      - "GITEA_MAILER_PROTOCOL=${GITEA_MAILER_FROM:-smtps}"
     secrets:
       - smtp_password