''re When I use IMAP/SMTP incoming/outgoing servers, sending message fails: it asks me to enter another password, but does not give me a prompt to enter it'' It's helpful if you posted an image of the error. All password prompts usually occur because either you have not saved the password in Thunderbird OR the server is refusing the currently saved password. You cannot alter or modify any password in Thunderbird. Passwords can only be created and modified/reset if you logon to your webmail account via a browser. Then you can update the stored password in Thunderbird to match the new password. Some servers use the Normal Password - same one you use to access webmail account. Other server insist you have to create a secure app password sometimes called an app generated password that you use only in Thunderbird for that specific email address. There are also some servers that use OAuth tokens, so a normal password is only ever used the once when setting up token and thereafter server uses the token. What servers are you talking about? Please post an image of your outgoing server settings. Include this data: * Help > Troubleshooting Information * Scroll down to 'Mail and News Accounts' section Then either copy all data and paste it into this support question. Do not leave out some of the data because there are cases when people have more than one using account using same server and this data will tell if that is the case, so we can check you are sending using the correct smtp. Or can post an image showing the data.