Good afternoon. I am a computer scientist by profession and I have a lot of experience with computers. I have Thunderbird version 78.6 installed on a freshly installed Windows 10 computer. It had been working perfectly for several months and now right now it says that it fails in the sending of emails, without giving more details, only that it fails in the assembly of the message. I've tried everything: delete account from send.one.com, uninstall thunderbird, delete user folders and program files, pass ccleaner, reinstall thunderbir and add account from send.one.com again, add account from another service provider (gmail), different smtp ports with different security, windows updates ... In short, everything I have found in thunderbird help, what I have read from the internet and much more that has occurred to me. Any help is appreciated please. Thank you very much in advance.