I'll try this one more time
Could anyone answer my question regarding this issue? I want to allow one single email adres to be able to mail to all domainnames possible, but the rest mustn't be able to. So, firstname.lastname@example.org
would be able to send email to wherever he desires to, yet email@example.com
shouldn't be able to. I already managed to configure Postfix so there are only 3 domains allowed to email through the system. They may send email to the same 3 domains only.