Cannot encrypt email message content and attachment

I’ve just downloaded and installed the free personal digital cert and installed it on Windows 7 64-bit with Outlook 2010 64-bit.

I am able to digitally signed an email (could see that the cert was installed in the Personal Store on the computer just fine and it is valid), but I am unable to encrypt the email and attachments. I keep getting the following error from Outlook, regardless of whom I send an email to - internally and externally to my organization.

…“Microsoft Outlook had problem encrypting this message because the following recipients had missing or invalid certificates, or conflicting or unsupported encryption capabilities.” The Continue button is grey out, and the only options is to send the email “Unencrypted” or “Cancel”.

  • I’ve tried encryption of “3DES” and “AES-256” and that made no difference.

  • I’ve tried intalling the same cert on a Windows XP SP3 and Outlook 2010, and got the same error too

Has anyone encountered this issue before and please share the fix if you know it.

I want to test out this digitally signed and encryption stuff before recommending my company to purchase this product, so I would greatly appreciate some help from the Comodo folks.




Check out how email certificates work here:,128,96


Thanks so much for your reply. I was finally able to send encrypted and signed emails using the info from the link you provided.

Greatly appreciated.