wordpress not sending email

I do apologise if this topic is answered elsewhere, or has been rehashed over and over again, but I’m at the point of tearing my hair out with it.

I do need my website to successfully send emails.

My system details are as follows:

Apache 2.2.15 (CentOS 6.4), PHP 5.3.3, MySQL 5.1.69.
Wordpress 3.5.2 with Kit MacAllister’s Brunelleschi 1.6.5

The site is here: http://ebookswest.com.au

On initial installation, when I entered my new admin details I actually did receive an email advising me of the fact, but nothing since.

I have tested and tested email but while it says ’email sent’ I never receive any.

I have checked SMTP Port 25 from my server firewall through the router all the way through my ISP, and it’s open all the way through.

I have run an open port checker with the result: ‘Port 25, SMTP is open and accepting connections’.

I have telnet into the server via PuTTY with the result: ‘220 s3.site211media.com.au ESMTP Sendmail 8.14.4/8.07 +0800’.

I have sent email from both KMail and Thunderbird mail clients on the server and they are delivered almost immediately.

Please, somebody explain to me how I can get WordPress to send emails finally.

Alternatively, please direct me to an already resolved post.

Thanks in anticipation, and kindest regards to all here,

Gil