When does it ask for a password (at startup, sending mail or receiving mail?), and what does the prompt look like? Did it work before, or have you just set up Thunderbird? Can you send mail? Who is the email provider? I ask because it can be a password for retrieving mail, one for sending mail, or a master password. If you can, please see [[How do I create a screenshot of my problem?]] for info on creating a screenshot. (Please don’t mind it was written for Firefox.) In general, everyone needs a password at least to retrieve mail, or anyone could access your email. Most providers require one for sending one too. A master password needs to be set manually, and nowadays, many providers require to set up an "app password" too.