as the passwords used are all set by your mail provider, asking here will not help you. Normally the incoming and outgoing passwords are the same, but requests for passwords out of the blue are usually defective anti virus / Firewall, not actually a password issue at all. However if you click to save a blank password when prompted Thunderbird may well "forget" the password that has been saved in the password manager. I suggest Restart the operating system in '''[http://en.wikipedia.org/wiki/Safe_mode safe mode with Networking]'''. This loads only the very basics needed to start your computer while enabling an Internet connection. Click on your operating system for instructions on how to start in safe mode: [https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode Windows 10], [http://windows.microsoft.com/en-us/windows-8/windows-startup-settings-safe-mode Windows 8], [http://windows.microsoft.com/en-us/windows/start-computer-safe-mode#start-computer-safe-mode=windows-7 Windows 7], [http://windows.microsoft.com/en-us/windows/start-computer-safe-mode#start-computer-safe-mode=windows-vista Windows Vista], [http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/boot_failsafe.mspx?mfr=true" Windows XP], [http://support.apple.com/kb/ht1564 OSX] ; If safe mode for the operating system fixes the issue, there's other software in your computer that's causing problems. Possibilities include but not limited to: AV scanning, virus/malware, background downloads such as program updates.