Alias Domains not added to rejectnonexist

[[email protected]]

When I have a domain and 1+ Alias domains e.g. example.com and Alias ex.com.
I disabled the catchall in plesk but only the domain example.com is added to the rejectnonexist file, the domain ex.com is not added and therefore mails to this domain are accepted although it should be rejected (can produce high load although catchall is deactivated).
I had to (and will have to on every change) edit the file manually so the alias domains are present too, in order to reduce my load.