When I open up my Thunderbird to get emails I keep getting getting error code 0x80570015. I can't see attachments and cannot respond to emails. Also cannot delete emails. I Iooked it up to see how to fix it and they say to remove the "lightning" add on. When I go under tools and look for this add on, it is not there. In fact it doesn't seem that I have any add-ons. Something to do with the calendar which I don't even use. It says Thunderbird is up to date. Could you please give any advice how to fix it. Thanks, Matt