Verify organization key

Hi

For internal Symantec Encryption Desktop users all  SEMS SKMS keys are marked verified on the client, but when we share the public key to an external user  it shows as not verified, even if we include the public part of the organization key. I'm guessing it is becuase the organization key is not signed and verifed?

How do I sign the Organization key so it is trusted by users outside our organization? The organization key we use was automatically created during installation.

Torb