Email alerts in html

In ces_offerswants.install:

function mymodule_enable() {
  $current = variable_get('mail_system', array('default-system' => 'DefaultMailSystem'));
  $addition = array('mymodule' => 'MymoduleMailSystem');
  variable_set('mail_system', array_merge($current, $addition));
}

function mymodule_disable() {
  $mail_system = variable_get('mail_system', array('default-system' => 'DefaultMailSystem'));
  unset($mail_system['mymodule']);
  variable_set('mail_system', $mail_system);
}

(Needs in hook_update too, for sites in production)

In offerswants.module:

class MymoduleMailSystem extends DefaultMailSystem {
  public function format(array $message) {
    $message['body'] = implode("\n\n", $message['body']);
    $message['body'] = drupal_wrap_mail($message['body']);
    return $message;
  }
}

(This is avoiding function html_to_text() in class DefaultMailSystem)