Collecting mail for multiple domains in one single mailbox

[Henning Holly]

Hi,

let's say I have two domains, domain.de and domain.net. Now I want to
collect all mail for user at domain.de and user at domain.net in the mailbox
of user at domain.de.
For this setup, which parameter do I have to change? I added the domain
in my ldap directory and read here
http://www.postfix.org/VIRTUAL_README.html about virtual aliases and
found out that the virtual_alias_domains should be the parameter to go.
I changed it to

virtual_alias_domains = $virtual_alias_maps, domain.net, domain.de

but this gives me a "Recipient address rejected: User unknown in virtual
alias table;". The same occurs if I add those domains manually to
mydestinations.

Please give me a hint how to achieve this.

Henning