'''1.''' Is thunderbird working ok on other mail account or is this the first mail account? * Exit Thunderbird * Access Firewall * Set up Thunderbird program as an allowed program otherwise the firewall may block ports so Thunderbird cannot access server. '''2.''' What server are you trying to connect to ? eg: gmail, yahoo, comcast, BT etc ? In Thunderbird have you set up to allow cookies ? * Settings > Privacy & Security * Select 'Accept cookies from sites' Normally you use the same password you use to access webmail. Have you actually logged on to the webmail account to check the password is good? If no then please check the password is good and gets you access to webmail account. If using Authentication Method : Oauth then you need to switch off 2 step verification and also make sure no other app id using the 'localhost' eg: Apache. If something is using localhost then switch it off until account is set up. But some servers need other settings selected and some say you have to general a secure mail key or app generated password. Xfinity requires you select a checkbox to allow thirdy party apps access to server: https://www.xfinity.com/support/articles/third-party-email-access I could be guessing all day long.... So please tell us what server you are trying to access ? What comes after the '@' in your email address?