I can send messages in HTML format, but can only recieve them in Thunderbird as plain text. To see a message in HTML format, I have to avoid Thunderbird and read my message in web mail, but this is a serious inconvenience for me. I think problem began with installation of Enigmail add on, but problem persists even if I disable Enigmail or restart Thunderbird in safe mode. My operating system is Mac OSX (Mavericks). This is the second time I have asked this question. I got no response the first time.