I was reading :

why o why is .local used in the examples and not example.com?

.local is a registered TLD for Apple’s mDNS (zeroconf/avahi-daemon)
which is by default installed on for example ubuntu

Result failures in resolving.

please read:
https://tools.ietf.org/html/rfc6761 (Special-Use Domain Names)

what MS is saying about this.
( source : https://social.technet.microsoft.com/wiki/contents/articles/34981.best-practices-for-internal-ad-domain-and-network-names.aspx )

Dummy DNS name vs official DNS name

In the past, lots of people chose to use a dummy, unofficial TLD (top-level-domain) for their internal network, like domain.lan, domain.local of domain.internal (and also domain.internalhost)

But this can get you in serious trouble. Because these names are not supported by internet standards, the most important RFC on this is: RFC 2606 Jump (http://tools.ietf.org/html/rfc2606 Jump ) This RFC standard is very explicit on choosing domain names for private testing and documentation

But also for documentation some 2nd level domains are reserved

As you can see, these names are created for testing and not for production.

Plus, if the public naming standards change or additional names are released you might be using a name you don’t own and that can be routed to the internet, which conflicts with the initial use. Therefore, the technical conclusion is fairly straight forward: register a public DNS name and use it for your internal DNS resolution. So the use of <yourinternaldomain>.be is technically correct but it doesn’t stop there. There are some important consequences. Allow me to take the discussion a step further. You have to make a choice on the DNS zones:
•using a single DNS zone
•Using subdomains
•using different DNS zones

Now why am i saying this. For example: samba4 + kopano + kerberos auth and NOT useing .local helps in less problems.

Thanks for reading.