Email sending with markup

Yes, these follow-up mails doesn't seem to support HTML. You have to write them in plain text for now.

To send html emails, and fix the email showing the markup as you describe, change

function uc_followup_mail($key, &$message, $params) {
  $message['subject'] = $params['subject'];
  $message['body'] = wordwrap($params['body']);
  if (variable_get('uc_followup_bcc', '')) {
    $message['headers']['Bcc'] = variable_get('uc_followup_bcc', '');
  }
}

TO

function uc_followup_mail($key, &$message, $params) {
	
  $headers = array(
    'MIME-Version' => '1.0',
    'Content-Type' => 'text/html; charset=UTF-8; format=flowed',
    'Content-Transfer-Encoding' => '8Bit',
    'X-Mailer' => 'Drupal'
  );
  foreach ($headers as $key => $value) {
    $message['headers'][$key] = $value;
  }
  
  
  $message['subject'] = $params['subject'];
  $message['body'] = $params['body'];
  $message['subject'] = $params['subject'];
  $message['body'] = wordwrap($params['body']);
  if (variable_get('uc_followup_bcc', '')) {
    $message['headers']['Bcc'] = variable_get('uc_followup_bcc', '');
  }
}

I believe you can enable HTML emails site-wide using the Mimemail module.

I don't think this is particularly an issue with this module. I haven't looked into it very deeply, though, so if I'm wrong reopen the ticket. Just trying to clean up these old issues a bit.