This could be a problem with the server's configuration, or it could be someone trying to impersonate the server.
   If you have connected to this server successfully in the past, the error may be temporary, and you can try again later.

Since updating Windows 10 to version 1803 I am now having e-mail problems. I don't see how they can be related but with the complete and utter mess created after the installation (all files and folders moved to a hidden location in my computer) I am now having problems in sending e-mails. My e-mails are checked using the Mailwasher Pro programme before downloading through Thunderbird. This works perfectly OK but when I come to send e-mails, I get the message below. Can anyone suggest a solution to this? Secure connection failed accounts.google.com uses an invalid security certificate. The certificate is not trusted because the issuer certificate is unknown. The server might not be sending the appropriate intermediate certificates. An additional root certificate may need to be imported. Error code: <a id="errorCode" title="SEC_ERROR_UNKNOWN_ISSUER">SEC_ERROR_UNKNOWN_ISSUER</a> This could be a problem with the server's configuration, or it could be someone trying to impersonate the server. If you have connected to this server successfully in the past, the error may be temporary, and you can try again later.