Can you please built in S/MIME support out of the box to claws-mail and make settings similar to the GUI of other popular email clients? I found http://www.claws-mail.org/faq/index.php/S/MIME_howto on Windows 7 with gpg4win impossible to set up.
Signing an email with S/MIME on Windows 7 in Claws Mail version 3.14.0 with Gpg4win Version 2.3.3 gives error Cannot sign: General error (1). According to http://www.claws-mail.org/faq/index.php/S/MIME_howto this "usually means that there's something wrong with the gpg-agent (e.g. not running or wrong environment)." I seem not to find out how to adjust the S/MIME howto to Windows 7. What works though is verifying a signed S/MIME email. How did you set it up on your Windows 7 machine?