apt-get install postfix
service postfix start
apt-get install mailutils

Отправим тестовое письмо

echo «BODY» | mail -s «SUBJECT» мое_мыло@gmail.com

После этого можем отправить письмо посредствам PHP

Код:

<?php
     $to = 'send_to@email.com';

    $subject = "Thank you for contacting Real-Domain.com";
    $message = "
    <html>
    <head>
    </head>
    <body>
    Thanks, your message was sent and our team will be in touch shortly.
    </body>
    </html>
    ";
    $headers = "MIME-Version: 1.0" . "\r\n";
    $headers .= "Content-type:text/html;charset=utf-8" . "\r\n";
    $headers .= 'From: admin@mail.ru' . "\r\n";

    // SEND MAIL
    if(mail($to,$subject,$message,$headers)){
    	echo 'Hello, my friend!';
    }

?>