Internal Domain Names (good or bad?)

Muddle,

I'm not sure this is really an 'apple' question as this it more to do with security and network traffic for network architectue. You will find some good stuff on this site. http://www.networkcomputing.com/

Personally I'd stick with the same name from a user's perspective, independent of whether you're using separate DNS zones internally.

Using mail as an example, you might configure 'mail.domain.co.uk' as the hostname for your mail server.

By publishing that name in both the internal and external DNS you only need to tell users to configure their mail client to talk to mail.domain.co.uk and they'll always get connected. The magic of DNS means they'll resolve the public IP address if they're outside the network, and the private IP address if they're in the office (or on VPN, etc.). Now users don't need to maintain separate mail profiles for internal and external accounts.

Now, whether or not mail.domain.co.uk is the actual hostname of the machine on the internal network is a different matter altogether. This could easily be CNAME'd to mailserver.office on the internal zone, allowing you to maintain the .office zone on the inside network which has advantages in that you know you should never serve .office to external clients.

Personally, in my network, there are no externally-visible hostnames that match the actual machine names.