Active Directory Name Space planning

Should you set your 2000 AD name space to be the same as your existing domain name when migrating
to 2000?

Example

Single site with a single domain
Existing emails are user@abccorp.co.uk
Existing web site is www.abccorp.co.uk
Existing NT4.0 domain is abcuk

Any ideas on the preferred AD name space
and why?

Thanks for your time