$re = '/[^m]>/';
$str = '<test@gmail.com>
>Lorem ipsum dolor sit amet,<test@gmail.com> consectetur
>adipiscing elit. Integer nec >
>odio. Praesent libero. Sed cursus ante dapibus diam. Sed nisi. Nulla
>quis sem at nibh elementum imperdiet.Duis sagittis ipsum. Praesent
>mauris. Fusce nec tellus sed augue semper porta. Mauris massa.
>Vestibulum lacinia arcu eget nulla. Class aptent taciti sociosqu.
<test@gmail.com>';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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