Postfix NIS lookup error

If you install postfix in debian (3.1) by using apt-get install postfix, then most likely there will be an NIS lookup error such as :

Jan 30 09:48:01 localhost postfix/smtpd[11719]: warning: dict_nis_init: NIS domain name not set - NIS lookups disabled

To eliminate the error, go to main.cf and erase or comment out any references to nis: such as aliases = nis:alias.name