I upgraded to Windows 10. I used Thunderbird as my email application. I have four email accounts, the primary being tedsch47@gmail.com. I have three secondary accounts, tedsch47@hotmail.com, tedsch47@yahoo.com and tschroeder75@yahoo.com. I no longer can download email to the secondary accounts and I cannot create a new account. When trying to create a new account, I get an error message stating that my email address or password is invalid. I don;t want some convoluted fix where I have to copy a gazillion files and do all kinds of other things. Mozilla needs to fix this problem. I like Thunderbird as my email app but if I can no longer use it, I will have to look for another app.