I'm going to promote a server to a DC and install AD. I read here about the confusion re internal and external names. I understand I should give the internal one an extension of .local so DNS can understand it. But is it necessary that the first part of this name match what is our external name? I.e., we're not doing a website, we just have a domain name registered out there for email, which I think is long and cumbersome and would rather not use internally. So can I name my internal one abc.local and the one to be used just for email is blahblahblah.com?