Ubuntu – sending php mail from localhost

I have installed php, mySQL, postfix and sendmail and have set up a simple email script on my local host server. mail() returns 1 (TRUE) when I send an e-mail, however the email does not arrive at the destination.

Installation

The mail functions are part of the PHP core. There is no installation needed to use these functions.

Requirements

For the mail functions to be available, PHP requires an installed and working email system. The program to be used is defined by the configuration settings in the php.ini file.

Runtime Configuration
The behavior of the mail functions is affected by settings in the php.ini file.

Mail configuration options:

Name            Default     Description                                         Changeable
sendmail_path   NULL        Unix systems only: Specifies where the sendmail
                            program can be found (usually /usr/sbin/sendmail
                            or /usr/lib/sendmail)                               PHP_INI_SYSTEM

I found it at /usr/lib/sendmail however, I can not find the configuration file, which is where I assume my problem is, as I have not told anything which server I am using to send my mail through.

If anyone can help me I would be grateful.