This add-on requires that your host has ports 995 or 993 open – these are the industry standard IMAP and POP3 ports. However, some hosts inexplicably keep these two ports closed. If you are using these hosts you cannot use this add-on. Instead we recommend that you find a different host that will allow access to your email server via these ports.
We know that the hosts listed below block ports 995 and 993. This is not an exhaustive list by any imagination. So, if you know that our host blocks these ports please let us know so we can update our list.