diff --git a/roles/mail_server/templates/main.cf.j2 b/roles/mail_server/templates/main.cf.j2
index b3ab8923ce9e29cd6743e52ae5d5a328290233ca..015c86190e3fcf9c3e840599683b2d8d5812086f 100644
--- a/roles/mail_server/templates/main.cf.j2
+++ b/roles/mail_server/templates/main.cf.j2
@@ -77,3 +77,6 @@ notify_classes = resource, software, 2bounce
 # Fall-back to using native lookups (/etc/hosts etc) if DNS lookup fails. Useful
 # for local overrides of mail servers.
 smtp_host_lookup = dns, native
+
+# Explicitly set maximum allowed mail size that should be accepted.
+message_size_limit = {{ mail_message_size_limit }}