Hello there We have read that question We try to help you. You cannot send messages ,oke. Did you check if these messages do have their good smtp configuration onboard. What anti virus do you use?is it possible to stop scans from antivirus programs that are for email programs like thunderbird in that anti virus program you can also go for the option to turn off the vpn to. Some bad add ons can disturb these outgoing mails from getting out to the receiver. You can use the troubleshoot mode to configure and see if there is really a bad add on there in the list that causes that and more things? You can try to start thunderbird into that troubleshoot mode with add ons turned off. So if these messages can be send again in that troubleshoot mode, it worked. If you did check these subjects and they are all good. If you cannot send messages but still only can receive messages. It is possible that you can be on a spam or blacklist somehow? Did you received some pop ups or screen boxes with error message s? Similar to what I just did described? Try to send me that screenshot . https://support.mozilla.org/en-US/kb/how-to-make-screenshots https://support.mozilla.org/en-US/kb/troubleshoot-mode-thunderbird Greetings googleThunderbird.