<blockquote>I reinstalled Thunderbird without email address.</blockquote> Not sure what you mean. You may have become confused by the wording used by Thunderbird here, because it looks like you <i>do</i> have an existing email account… with your email provider, which is what Thunderbird is referring to… Anyway, you may have to enable access to third party email clients as described here first, you didn't mention having already done that: https://www.xfinity.com/support/articles/third-party-email-access I think you're then supposed to set up the account in Thunderbird as described here. You may have to <b>Configure manually</b> the account if automatic configuration doesn't work: https://www.xfinity.com/support/articles/email-client-programs-with-xfinity-email Post a screenshot of your account settings if that still doesn't work in case there is something you could be missing.