Hello, I have a qualified certificate for electronic signature installed on my PC and added to Thunderbird, but when I want to electronically sign an email I send, it doesn't work and it gives me this message: Send message failed. You have selected an electronic signature for this message, but the application could not find the corresponding certificate specified in the account settings for mail and newsgroups, or the certificate has expired. Do you know what this could be? Thank you for your reply. Have a nice day Daniel Suk, e-mail: dan.suk@volny.cz