When you send an encrypted message to a recipient that is located in the Global Address List, you may receive the following error message:
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
where e-mail recipient represents a recipient that you are sending an e-mail message to.
Error: "Microsoft Outlook had problems encrypting this message because the following recipients had missing or invalid certificates or conflicting or unsupported encryption capabilities."
This problem can occur because when Outlook searches the Global Address List for encryption certificates, it searches for three properties in the following order:
If the Tagged-X509certs property is invalid (for example, if it is expired, corrupted, and so on), Outlook does not fail over and query for any valid X509-certs or User-certs properties. For example, if the Tagged-X509certs property is missing and the X509-certs property is invalid, Outlook does not fall back and query the User-certs property, even if the property is valid. This behavior prevents the user from sending encrypted mail to other users who have an invalid digital certificate.
To resolve this problem, go to one of the following Microsoft Web sites:
Microsoft Outlook 97
Microsoft Outlook 98
Microsoft Outlook 2000
Microsoft Outlook 2000 SR-1
The fixes above do not cover Windows XP, Office XP or Outlook 2002. For information about these e-mail programs, please contact Microsoft.