I seem to have fixed it. I had some old proxy information configured in Thunderbird. It was set to Direct Connect so it was not set to use the proxy but once I deleted all the proxy information it's working every time, even after a restart of Thunderbird.
I seem to have fixed it. I had some old proxy information configured in Thunderbird. It was set to Direct Connect so it was not set to use the proxy but once I deleted all the proxy information it's working every time, even after a restart of Thunderbird.