We are about to set up SBS 2011 at my small company < 10 users. My collaborator wants to name the SBS domain "example.local" . I'm of the opinion we should name the SBS domain "corp.example.com" and setup DNS so the "corp" record is a NS record to the SBS server's private IP.
FYI: "Example.com" isn't the real domain name and while the website is hosted outside our office, email will be stored on the SBS server in our office after passing though a spam filtering smart host hosted elsewhere too.
Best Answer
Personally, I'd go with example.local, which according to Wikipedia is Microsoft's recommended naming convention.
I can't find any info to back this up, however Microsoft do have an article regarding naming a domain, which should be useful to you.
I've done many installs using this naming convention, and it give you the flexibility to be be able to assign internal and external DNS names to any system on the network as required. (e.g. test.example.local would point to the internal IP address, and test.example.com would point to its external IP address - assuming it is accessible to the outside world of course).
Note that you might find if you try to use test.example.com internally it won't work by default, but you can add another internal DNS zone (test.example.com) with a default record that points to the IP used by test.example.local, this way, test.example.com works internally and externally.
I also maintain systems for a customer that shares a .com internally and externally, and I'm constantly struggling with the duplicate DNS namespaces.
Edit: also note that .local is not a valid TLD according to RFC2606