problems encrypting this message

Hi
i’m trying to use email certificate and encryption in Microsoft outlook but while sending a email getting popup msg which says

“Microsoft Outlook had problems encrypting this message because the following recipients had missing or invalid certificates, or conflicting or unsupported encryption capabilities: e-mail recipient”

i’m using Microsoft Outlook 2003 and COMODO free email digital cert.

pl. help
THANKS

Hi,

As stated in error message, Both the sender/recipient must have valid email certificate to send and receive encrypted mails.

Please visit the following link for information on this
https://support.comodo.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=228&nav=0,32
https://support.comodo.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=229&nav=0,32