Can sign but cannot encrypt email using a valid S/MIME certificate

Dear all, I have obtained numerical certificates of national certification authority in Czech Republic (ICA). 1/ I have imported the certificate into Mozilla Thunderbird > Account Settings > Security > Digital Signing. - It shows Software Security Device:TwinsQS 10/07/2015. - Digitally sign mes

Can sign but cannot encrypt email using a valid S/MIME certificate

Dear all, I have obtained numerical certificates of national certification authority in Czech Republic (ICA). 1/ I have imported the certificate into Mozilla Thunderbird > Account Settings > Security > Digital Signing. - It shows Software Security Device:TwinsQS 10/07/2015. - Digitally sign