You have not provided much information, so I'm providing some general basics. Are you trying to create a new mail account in Thunderbird for an existing email address? If yes: What server are you trying to connect to eg: outlook, gmail, comcast, BT, yahoo ? Check: '''1. '''Firewall - Exit Thunderbird and Access the Firewall. The Firewall may the default that came with computer or it may be controlled by an Anti-Virus program you installed. Thunderbird program must be set up as an allowed program otherwise the Firewall may block access to internet. '''2.''' VPN Most servers do not like VPN because it disguises your IP address, so servre thinks someone may be hacking the account. If you have a VPN or even if you ar not sure, please check, some Anti-Virus have VPN which might be auto switched on. Switch off any VPN. '''3. '''Many webmail accounts require that you enable POP and/or IMAP so that those types of accounts can be set up. Logon to webmail account via a browser and see if there is a setting you need to select to enable Imap and Pop. Logon to webmail account anyway because this will provce to you that the password works. '''4. ''' email addresses that use these servers : outlook,gmail and yahoo 1) - Make sure nothing is using the 'localhost' - eg: programs such as Apache Xampp or similar. Often this effects people who create or maintain websites. Switch off any program that uses the 'localhost'; you can enable it again after setting up OAuth token. 2) - To connect to these servers which use 'Authentication Method: Oauth2', you need to make sure the following is set up in Thunderbird. * Settings >Privacy & Security * Under 'Web Content' * Select checkbox 'Accept cookies from sites' * Accept third party cookies: 'Always' You can also add the appropriate server data : click on 'Exceptions' button Example: For gmail enter: https://accounts.google.com For Microsoft enter eg: outlook.com, hotmail.com, live.com, msn.com '''Process to create a mail account:''' * Click on the 'Menu app icon' (it h as 3 horizontal lines) * Select 'New Account' * Select 'EMail' * Enter Name, Email address, Password and select checkbox to Remember Password * Click on 'Continue' Thunderbird attempts to locate server settings as it knows most of the more common server settings. By default Thunderbird also tries to set up IMAP. If creating for gmail, outlook or yahoo servers then when creating the account you will get prompted by the relevant server eg: google to enter password and then click on 'Allow' to permit Thunderbird access to server. If you still have a problem then you need to provide more information. # What OS are you using? # What version of Thunderbird are you using? # Are you setting up IMAP or POP ? # What server settings are you trying to use? # Provide an image showing error.