openX广告服务器未在电子邮件正文中显示横幅广告

i have created a banner in openx and linked it with zone. Type of zone is Email/Newsletter zone and get its invocation code and paste its code in email body but i don't get banner in email body at receiver end. It gives error showing all invocation code instead of banner

Email Body :-

<htm>
    <body>
        <a href='http://mysite/openx/www/delivery/ck.php?zoneid=9' target='_blank'>
            <img src='http://mysite/openx/www/delivery/avw.php?zoneid=9&amp;cb=452745' border='0' alt='' />
        </a>
    </body>
</html>

i have also used simple php mail function to send mail.

Links for inserting should be similar with this:

<a href="http://mysite/openx/www/delivery/ck.php?n=__CODE__&cb=__RAND__">
    <img src="http://mysite/openx/www/delivery/avw.php?n=__CODE__&cb=__RAND__&zoneid=__ZONEID__"/>
</a>

where:

__CODE__ - 8digits hash, __RAND__ - random number, __ZONEID__ - zoneId.

In both urls CODE and RAND must be equal