Call to undefined function wp_email()

I have a custom product form inquiry create and all of its data are sent through AJAX. The problem is although I included the wp-load.php file for wp functions and pluggable.phpfile for wp_email function, it still show an error:

Fatal Error: Call to undefined function wp_email()

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This is my code for inquire.php inside a folder that sends the email inquiry:

require('../wp-load.php');

require('../wp-includes/pluggable.php');

$to = 'email@email.com';
$subject = 'Product Inquiries';
$message = '
    <table width="99%" cellspacing="0" cellpadding="1" border="0" bgcolor="#eaeaea">
        <tbody>
            <tr>
                <td>
                    <table width="100%" cellspacing="0" cellpadding="5" border="0" bgcolor="#ffffff"><tbody>
                        <tr bgcolor="#eaf2fa">
                            <td colspan="2"><font style="FONT-FAMILY:sans-serif;FONT-SIZE:12px"><strong>Name</strong></font></td>
                        </tr>
                        <tr bgcolor="#ffffff">
                            <td width="20">&nbsp;</td>
                            <td><font style="FONT-FAMILY:sans-serif;FONT-SIZE:12px">'.$your_name.'</font> </td>
                        </tr>
                        <tr bgcolor="#eaf2fa">
                            <td colspan="2"><font style="FONT-FAMILY:sans-serif;FONT-SIZE:12px"><strong>Email Address</strong></font></td>
                        </tr>
                        <tr bgcolor="#ffffff">
                            <td width="20">&nbsp;</td>
                            <td><font style="FONT-FAMILY:sans-serif;FONT-SIZE:12px"><a target="_blank" href="mailto:'.$your_email.'">'.$your_email.'</a></font> 
                            </td>
                        </tr>
                        <tr bgcolor="#eaf2fa">
                            <td colspan="2"><font style="FONT-FAMILY:sans-serif;FONT-SIZE:12px"><strong>Phone</strong></font></td>
                        </tr>
                        <tr bgcolor="#ffffff">
                            <td width="20">&nbsp;</td>
                            <td><font style="FONT-FAMILY:sans-serif;FONT-SIZE:12px">'.$your_phone.'</font> </td></tr>
                            <tr bgcolor="#eaf2fa">
                                <td colspan="2"><font style="FONT-FAMILY:sans-serif;FONT-SIZE:12px"><strong>Product Link</strong></font></td>
                            </tr>
                            <tr bgcolor="#ffffff">
                                <td width="20">&nbsp;</td>
                                <td><font style="FONT-FAMILY:sans-serif;FONT-SIZE:12px"><a target="_blank" href="'.$prod_link.'">'.$prod_name.'</a></font></td>
                            </tr>
                            <tr bgcolor="#eaf2fa">
                                <td colspan="2"><font style="FONT-FAMILY:sans-serif;FONT-SIZE:12px"><strong>Message</strong></font></td>
                            </tr>
                            <tr bgcolor="#ffffff">
                                <td width="20">&nbsp;</td>
                                <td><font style="FONT-FAMILY:sans-serif;FONT-SIZE:12px">'.$your_message.'</font> 
                                </td>
                            </tr>
                            <tr bgcolor="#eaf2fa">
                                <td colspan="2"><font style="FONT-FAMILY:sans-serif;FONT-SIZE:12px"><strong>Referred By:</strong></font></td>
                            </tr>
                            <tr bgcolor="#ffffff">
                                <td width="20">&nbsp;</td>
                                <td><font style="FONT-FAMILY:sans-serif;FONT-SIZE:12px">'.$referred_by.'</font> 
                                </td>
                            </tr>
                        </tbody>
                    </table>
                </td>
            </tr>
        </tbody>
    </table>';
wp_email($to,$subject,$message);

Please help guys.. thanks..