Since yesterday afternoon, the Mail program of my macOS complains that it can validate the certificate of my imap server.
The weird thing is that I could access my imap mail account for months without problem. I renewed the certificate the 1 sept. The Let’s Encrypt X3 certificate is appended to the server certificate returned by my server.
Another weird thing is that if I restart the Mail program I can access my imap mails and macOS’s mail doesn’t complain. The warning started only since yesterday in the middle of the day. Never had a problem before. Does Mac mail skip certificate verification in this case ?
Could there be a MITM attack ? Mail asked me to trust the certificate, but I don’t do that unless I understand and I’m sure of what is going on. I’m a noob with macOS so I don’t know where to look up the CA. This happend at my work place.
I had a similar problem with thunderbird on windows and linux. But in this case it would just block all access. I had to add the Let’s Encrypt X3 certificate obtained from the Let’s Encrypt site. This happened at my workplace and at home. So I suspect there is a missing certificate in thunderbird.
This really doesn’t look right. How can we be sure we have the correct certificate and I’m not in a glasshouse ?