Active Directory Domain Name Convention

Question

Hi All
I'm creating a brand new domain for a new company I have just started at. We currently use Office 365 so sharepoint and Exchange are both in the cloud and our website is also outsourced.
I am now rolling out our first DC on Windows 2012 Server and I'm find conflicting reports on what naming convention I should use for AD with use with hosted exchange.
Most seem to point at using a subdomain of our main site, like corp.mydomain.com whereas I come from a background using Server 2003 where its always been mydomain.local
Can anyone advise me on this one and are there any additional thoughts around implementing with an existing Office 365 setup?

Answer 1

It seems that mydomain.local is recommended less often (if not discouraged) because certificates from a third-party CA will no longer accept internal domain names, like mydomain.local, in the near future.
Some links on this subject:
http://social.technet.microsoft.com/Forums/exchange/en-US/a460ee18-e674-4c14-b4e8-33afd9ddb2a0/change-local-to-com-to-resolve-ssl-certificate-mismatch?forum=exchange2010
http://www.digicert.com/internal-names.htm
http://exchangeserverpro.com/ssl-requirements-for-exchange-when-certificate-authorities-wont-issue-certificate/
In any case Office 365 will not interact with internal names. If you use such a name currently, you'd have to configure a UPN suffix allowing users to connect with the external name. This link might
explain it better:
http://www.messageops.com/documentation/office-365-documentation/active-directory-federation-services-design-planning-for-office-365
In particular:
"It is common for organizations to use one domain name internally and a different domain name externally. A best practice was to have your internal Active Directory domain name have a .local or a .corp suffix.  With Office 365, the UPN suffix must match
your external domain name which you have registered and verified within Office 365.  In these types of situations it is necessary to add a UPN (User Principle Name) suffix to the Active Directory."
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