I am running Thunderbird version 38.6.0. Since installing windows 10 I am having problems sending emails. Thunderbird downloads my emails with no problem, however when I go to send sometimes it works and sometimes it doesn't. When I click send, it looks like it is sending but will come back and ask for my password. Won't accept it. Then I go to tools/account settings and click on outgoing server. I reselect the smtp.centurytel.net item and go back and send will now work although sometimes it will ask for a password again and accept it this time. I have tried reloading thunderbird but that didn't solve the problem either.