I am developping a windows applciation in dotnet for a customer who uses Zimbra as their mail tool accross the network. The application has to create a list of contacts to email and put their email address into the BCC field on an email. A sample of the mailto command I am using is

This works fine where the default mail client is Outlook, Outlook Express or Thunderbird, but when the default mail client is Zimbra the cc and bcc fields are not populated by the data in the command. The other three fields (To, Subject and Body) are populated correclty. Does anyone know why Zimbra is unable to process the command fully?