Hi As the message says this could be wrong configuration or username or password. Please provide more information about what you are trying to do. Is this is your first time setting up this email account in Thunderbird? If not, was it working before and what changed? If this is a new email account where were you looking for the correct server settings to use? Is it POP or IMAP? Bear in mind, every email service has different settings. For first-time setup Thunderbird will try to set up the right settings for your email account - see this help page https://support.mozilla.org/en-US/kb/automatic-account-configuration Then for some types of email you may need to set up a token or two stage authentication - again that depends on which email service you use and what they require. Good luck with getting this going! Agnes