diff --git a/roles/mail_forwarder/molecule/default/group_vars/parameters-optional.yml b/roles/mail_forwarder/molecule/default/group_vars/parameters-optional.yml
index cc643b03c25e1630886fd286648f466ba9ac4260..f09e3c2d8eedd1a7693bbe3b3707c95c22094a40 100644
--- a/roles/mail_forwarder/molecule/default/group_vars/parameters-optional.yml
+++ b/roles/mail_forwarder/molecule/default/group_vars/parameters-optional.yml
@@ -2,6 +2,7 @@
 
 local_mail_aliases:
   root: "root testuser"
+mail_message_size_limit: 20480001
 smtp_from_relay_allowed: true
 smtp_relay_host: mail-server
 smtp_relay_host_port: 27