now actually allow the use of the custom var
diff --git a/templates/main.cf.erb b/templates/main.cf.erb
index a1ed4f7..70f7017 100644
--- a/templates/main.cf.erb
+++ b/templates/main.cf.erb
@@ -975,3 +975,7 @@
 content_filter =  scan:127.0.0.1:10026
 receive_override_options = no_address_mappings
 <% end -%>
+
+<% if @asf_mx_enabled -%>
+content_filter = <%= @asf_mx_content_filter %>
+<% end -%>