text/html content type for all wordpress mails

This filter always runs and makes wordpress and other plugin mails look bad.

mage-eventpress/inc/mep_functions.php:3729

if (!function_exists('mep_set_email_content_type')) {
    function mep_set_email_content_type() {
        return "text/html";
    }
}
add_filter('wp_mail_content_type', 'mep_set_email_content_type');