After installing the latest version of Thunderbird yesterday (1-27-2024), Thunderbird can no longer send out any emails on my PC using . I am a retired software engineer and contacted my service provider and after 2 hours of trying to find the issue, we have no clue. My email works fine through my service provider using my Apple products, and an alternate mail program on my PC, but not Thunderbird. Everything worked fine before the latest update. I did reboot my computer last night, and was able to send out 1 email, then it again stop sending. The following is the error message it always sends: Sending of the message failed. An error occurred while sending mail. The mail server responded: <ec2-15-181-97-27.compute-1.amazonaws.com[15.181.97.27]>: Client host rejected: Access denied. Before telling me this is a blacklist item, it is coming from Thunderbird and not my PC or service provider. Again other email software programs work with no problems on this PC and this started with the latest update. This is a Thunderbird problem. Please help. Dr. C. Lange