Digital signature

I installed Comodo’s certificate in my computer running MAC OS X Mavericks, and have successfully exported it to the PostBox mail client. As a result, I can send encrypted mails with no problem, but if I try to sign them (with or without encryption) PostBox answers “Sending of message failed. Unable to sign message. Please check that the certificates specified in Mail & Newsgroups Account Settings for this mail account are valid and trusted”. Everything seems ok in the OS side, but PostBox reports when viewing the certificate that it “Could not verify this certificate for unknown reason”. Can you help? Thank you.

Hello Camiguin

I too am using OS X Mavericks and Postbox.

I think you need to add the intermediate CA certificate that got things working for me, namely -
COMODO RSA Client Authentication and Secure Email CA

I got it from: Interestingly, having added it to Postbox I found that the OS X Key Chain Access key store also had a copy. You may want to try exporting it from Key Chain before resorting to downloading it?

I’ve also asked PostBox to add the missing certificate to their install package.