Linux, Apache, MySQL, PHP

return preg_match('/^(?:[\w\!\#\$\%\&\'\*\+\-\/\=\?\^\`\{\|\}\~]+\.)*[\w\!\#\$\%\&\'\*\+\-\/\=\?\^\`\{\|\}\~]+@(?:(?:(?:[a-zA-Z0-9_](?:[a-zA-Z0-9_\-](?!\.)){0,61}[a-zA-Z0-9_-]?\.)+[a-zA-Z0-9_](?:[a-zA-Z0-9_\-](?!$)){0,61}[a-zA-Z0-9_]?)|(?:\[(?:(?:[01]?\d{1,2}|2[0-4]\d|25[0-5])\.){3}(?:[01]?\d{1,2}|2[0-4]\d|25[0-5])\]))$/', $address);

function safe( $name ) {return( str_ireplace(array( "\r", "\n", "%0a", "%0d", "Content-Type:", "bcc:","to:","cc:" ), "", $name ) );}

=((<CR>|<LF>|0x0A/%0A|0x0D/%0D|\\n|\\r)\S).*=i

// Functions found from various sources

// www.nyphp.org/phundamentals/8_Preventing-Email-Header-Injection
// Pattern for filtering email addresses       --  '/^[^@\s]+@([-a-z0-9]+\.)+[a-z]{2,}$/i'
// Pattern for filtering fields such as names  --  '/^[a-z0-9()\/\'":\*+|,.; \- !?&#$@]{2,75}$/i'
function safe( $name ) {return( str_ireplace(array( "\r", "\n", "%0a", "%0d", "Content-Type:", "bcc:","to:","cc:" ), "", $name ) );}

// www.dreamincode.net/forums/topic/228389-preventing-php-mail-header-injections/
$reply_to = filter_var($reply_to, FILTER_VALIDATE_EMAIL);  if(!$reply_to) {...}
function sanitize(&$array) { foreach($array as &$data) $data = str_replace(array("\r", "\n", "%0a", "%0d"), '', stripslashes($data)); } } 


// PHP Mailer
// code.google.com/a/apache-extras.org/p/phpmailer/source/browse/trunk/class.phpmailer.php
// interesting to note that only FILTER_VALIDATE_EMAIL is used, FILTER_SANITIZE_EMAIL is not used
if (function_exists('filter_var')) { //Introduced in PHP 5.2
    if(filter_var($address, FILTER_VALIDATE_EMAIL) === FALSE) {
        return false;
    } else {
        return true;
    }
} else { 
    return preg_match('/^(?:[\w\!\#\$\%\&\'\*\+\-\/\=\?\^\`\{\|\}\~]+\.)*[\w\!\#\$\%\&\'\*\+\-\/\=\?\^\`\{\|\}\~]+@(?:(?:(?:[a-zA-Z0-9_](?:[a-zA-Z0-9_\-](?!\.)){0,61}[a-zA-Z0-9_-]?\.)+[a-zA-Z0-9_](?:[a-zA-Z0-9_\-](?!$)){0,61}[a-zA-Z0-9_]?)|(?:\[(?:(?:[01]?\d{1,2}|2[0-4]\d|25[0-5])\.){3}(?:[01]?\d{1,2}|2[0-4]\d|25[0-5])\]))$/', $address);
}
public function SecureHeader($str) { return trim(str_replace(array("\r", "\n"), '', $str)); } 


// PEAR Mail
function _sanitizeHeaders(&$headers)
{
    foreach ($headers as $key => $value) {
         $headers[$key] = preg_replace('=((<CR>|<LF>|0x0A/%0A|0x0D/%0D|\\n|\\r)\S).*=i', null, $value);
    }
}