set mailu version to 2.0.4

test/docker_mail/templates/mailu.env

@@ -17,6 +17,9 @@ SQLALCHEMY_DATABASE_URI=mysql://mailu:{{ mailu_db_pass }}@db/mailudb?charset=utf
 # Common configuration variables
 ###################################
 
+# Set mailu version 
+MAILU_VERSION=2.0.4
+
 # Set to a randomly generated 16 bytes string
 SECRET_KEY={{ mailu_secret_key }}