Different domain for Exchange 2003

I have a domain "xxxcity.local". I want to rename this domain to just "xxx" (without the city.local behind it). My question is this: If I change the domain name to "xxx", can I leave the exchange domain/email @xxxcity.com? My public is xxxcity.com. And if I can, will it cause a lot of headaches in the future? Forgive my lack of experience with Exchange server. Any help would be much appreciated.