Internal calling between domains

It can be done. You need a dialpan entry to transfer to EXT XML domain_name. So in your example, it will be

Code:
 12 XML pbx.domain.nl
1767852618081.png

I believe this will work.

It can also be done via a LUA script

session:transfer(extension, "XML", domain_name);
 
You need to develop a new custom dialplan. I recommend creating a tenant code and dialing [TENANT_CODE] + EXT. The phone will have [TENANT_CODE] + EXT, too. In the dialplan, you can extract the tenant code and assign the correct domain for transfer. Additionally, since this is a very specific feature, could you clarify your use case? I want to ensure you're heading in the right direction.
 
Of course, this is the idea:
Different elderly people living in the same street. They al have there own domain and everything is separated. but with this feature, they can call each other internal.
 
I would definitely use the the CODE for each tenant then. so instead of dialing 12 they would dial 1012 or 1112 where 10 and 11 are tenant codes.

However if they are calling each other and will never log in to the dashboard why not put theie ext in the same domain? Then they can just dial 12, 13 or 14 to reach each other