I'd very much like to use Thunderbird, however once it is installed and I try to import my Outlook 2013 data (contacts, folders, etc.) I receive this message: "Either there is no default mail client or the current mail client cannot fulfill the message request. Please run Microsoft Outlook and set it as the default mail client." I have followed all the steps I found online to ensure Outlook is in fact my default client, but the message persists. I have searched for Add-Ons and have come up empty. I am running Windows 8.1. I'm not going to switch over to Thunderbird if it can't do something as simple as move my data from one program to another on the same computer.