postfix sender restriction for mynetworks: limited domains only
 

Hello!
I use Postfix for SMTP. As a normal smtp server, my postfix receives mails from outside, if they are addressed to our existing mailboxes.

In case of 'mynetworks' (legal internal) senders, it receives and forwards mails addressed to the whole world.

For the latter, I'd like to restrict the sender domain for some valid domains only, like...@mycompany.com, ...@myfriend.com
The list of the valid sender domains is something like the unio of
- mydestinations and
- virtual_mailbox_domains

Thank you for your effort!