I installed Thunderbird a few days ago and it worked fine for about 12 hours and then I got repeated messages saying "certificate error" and that the app detected potential security threats. After that, I could no longer access my emails. My email provider is Telia, a company in Sweden, which is where I live. I called Telia but they say the problem is on your side. They are not aware of any security threats. Here is a screenshot of the warning. Should I go to the advanced settings and say I accept the risk and just continue? Thanks in advance. Barbara R, Sweden