$re = '/(?:\b(?:your|amazon\.com|shipped)\b.*){3}/i';
$str = 'Your Amazon.com order has shipped (#114-7286434-0549003)
Fwd: Your Amazon.com order of "Diva Ring Light Nebula 18..." has shipped!
Your Amazon.com order has shipped (#114-7286434-0549003)
Your Amazon.com order has shipped
Fwd: Your sdjcns order has deleted
Fwd: Your amazon order is cancelled
Your Amazon.in order (#171-8110001-7994703) of "Prestige Electric Kettle..." has been dispatched!
Your Amazon.in order #171-8110001-7994703 has been delivered
Your Amazon.in order #171-8110001-7994703 is out for delivery
Your Amazon.in order #171-8110001-7994703 has been shipped
Fwd: Your Amazon.com order of "Diva Ring Light Nebula 18..." has shipped!';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php