Ident authentication failed

v8.0.3
OS: SuSE 10.0 Pro

I am new to PostgreSQL but fairly familiar with other RDBMS' such as
Ingres, Informix and MySQL.

I am attempting to switch from using MySQL to PostgreSQL with postfix. I
have created the postfix user using createuser with a password but denying
the ability to create databases or other users. However when I attempt to
login even using psql:

    psql -W -U postfix

it prompts me for the password and I enter the one that user was created
with. The resulting error is:

    psql: FATAL: Ident authentication failed for user 'postfix'

I know I must be missing something simple but I cannot find it in the docs
or FAQs. Please point me in the right direction.

Thank you,
Lucky