Where to start. Your server is not noname. Withhold the actual email address if you like, but without the actual details of your server settings we will be guessing. Thunderbird 78 is no longer supported and it may be can no longer get mail from blue host. Without knowing what the setting to be used are I can only guess. I did look at blue hosts web site and they offer this very dated discussion. https://www.bluehost.com/help/article/email-application-setup Nothing there gives me a clie as to why you would be doing the things manually, but I would guess that you are using SSL/TLS and do not have an appropriate certifiect for your mail server. But I am guessing because I can not check the SSL of the server, or the DNS configuration. Perhaps you can, and report the results page links. https://www.immuniweb.com/ssl/ and https://intodns.com/ Than we have the issue that many folk with issues also have antivirus products that mess with mail and usually make getting it difficult by using self signed SSL certificates that Thunderbird knows nothing about. Failing that, you can log the connection https://wiki.mozilla.org/MailNews:Logging to find out exactly what error messages are being propagated, but not making it to the point you see them.