Alias Domains: transparently deliver to user at parent.domain

[Florian]

Hi all

In a setup with alias domains for a parent domain, is there a way to
transparently deliver mail addressed to an alias domain, to the mail
address in the parent domain, without explicitly listing them in a
user's contacts?

Example:

Parent domain: example.com
Aliases: example.org, example.net

deliver user at example.ORG, user at example.NET -> user at example.COM

Regards,
Florian