diff --git a/mail/docker-compose.yml b/mail/docker-compose.yml
index 4e11303..c63f925 100644
--- a/mail/docker-compose.yml
+++ b/mail/docker-compose.yml
@@ -1,5 +1,3 @@
----
-version: '3.9'
 services:
   mail:
     image: mailserver/docker-mailserver:14.0.0