I am attaching a screen shot of where I am up to now. So I was surprised to see that the account had been set up but continued on from there. On the window 'Set Up an Existing Account' it had failed to find the configuration and when I clicked 'Advanced config.' it simply closed the window. I had forgotten that it hadn't properly completed the setup. It is not a failure of Thunderbird.ĭeleted the account and started over. I have my doubts you will be able to add the suggested exception, but that is a matter for you and proton mail if it is the case. I think I can be sure that you will not be able to use TLS or SSL on the connection as there will not be a valid certificate for the 'server' (127.0.0.1) on the local machine. You might also find that your anti virus product blocks communication on the loopback address, that is how some malware communicates with itself so it is considered a 'risk' by some products.

I assume it is pretending to be an IMAP server, so I guess you will need to use the to configure the account in Thunderbird. Oh a google search indicates you are probably trying to connect to the proton mail bridge. So I assume you have some sort of security software that thinks is should be accessing your mail before you do. The server name is set to your local network card loopback address.

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