Thunderbird is just a program running on your computer. It is an email client program. It does not require any password to run Thunderbird. Thunderbird does not offer email addresses and does not have a server. You do not 'log in' to Thunderbird. The mail accounts you create in Thunderbird require an email address which you have already created. These email addresses may be provided by your Internet Service Provider or perhaps you have created a free one with eg: gmail or perhaps you own a domain and have a website and email addresses for that domain or maybe you have an email address supplied by a business or one you have purchased. In Thunderbird, those mail accounts use specific server settings in order to access the relevant server that receives and stores your emails. Each mail account will use a User Name = email address and will require a password to access the server. The password is the same password you use to access the webmail account for that email address. The webmail account is accessed via a browser. You can only set up a password or modify a password in the webmail account, then you use the same password when creating the mail account for that email address in Thunderbird. So the question is this: '''Q: '''Have you created a mail account in Thunderbird for an email address that already exists and it's been working for a while, but is now refusing to download emails or send emails? If yes: Post the following information. * Menu icon > Help > More TRoubleshooting Information * Scroll to 'Mail and News Accounts' * Ideally, upload an image showing all the data in that section in to this forum question * OR copy all the data information and paste it into this forum question. If you get an error message post an image of the error message. '''Q: '''Are you trying to create a new mail account for an email address? If yes: First you need to confirm you have a good password. Logon to your webmail account for that email address using a browser. If you can confirm you get access to your emails then you know the password is good and this is the password you use when creating the mail account. Please report back and confirm you can access the webmail account, so you know the correct password for that email address. '''Q: '''Do you get an error message when trying to create the account or download emails or send emails? If yes: post an image of the error message. re :WHEN I TRY TO LOG IN TO THUNDERBIRD, All the information I posted above is all about mail accounts created in Thunderbird that require passwords in order to access servers. You need to provide more information about where you try to "Login to Thunderbird"