Encryption fails as recipient has invalid,conflicting or unsupported...

My wife and I both run Outlook 2003, under Vista 32bit, and have successfully installed email certificates. Both can send certified emails. Each has saved the other’s contact details. When I try to send an encrypted email to her, I get the following error message:

“Microsoft Office Outlook had problems encrypting this message because the following recipients had missing or invalid certificates, or conflicting or unsupported encryption capabilitues”

Does anybody know how I resolve this?

Many thanks

I have also same problem with Office Outlook 2007. I have my own certificate and a friend of mine’s certificate too. When I am composing the email I click the Signature and Encrypt Button then the Send button and I get the same dialog "“Microsoft Office Outlook had problems encrypting this message because the following recipients had missing or invalid certificates, or conflicting or unsupported encryption capabilities” with a button saying to send it unencrypted.

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Comodo are looking into the issue for me via a support ticket. This is the latest solution offered. It has not solved the problem in my case, but it may be of use to others with different setups

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This error is not associated with the certificate itself, you need to check the settings in outlook as suggested in the technet article.

http://social.technet.microsoft.com/Forums/en-US/winserversecurity/thread/9ad86e6c-5f9f-4d84-9fdd-930929c8e91f

Unquote