Hello there huoyan 1231 We have read your message. We try to help you Check your Smtp settings for outgoing mail. Port numbers and security setting and your id name or email adres. See if they are filled in into the configuration settings of your software. If not change them if they are not oke in this good configuration description below in the text. https://support.mozilla.org/en-US/kb/cannot-send-messages https://support.mozilla.org/en-US/kb/cannot-receive-messages If there are more difficulties into thunderbird using. Try to start up in safe modus for thunderbird. It might be add ons that are bugging your software. https://support.mozilla.org/en-US/kb/troubleshoot-mode-thunderbird Configure for yourself with turning of and of the add ons. Also check you security settings for low and high settings for vulnerabilities. If being there you can check your settings with this form. https://support.mozilla.org/en-US/kb/manual-account-configuration Greetings Firefox volunteer