If a Symantec Encryption Desktop email user receives an s/mime signed email with the sender's separate signing and encryption certificates attached, only the signing certificate not the encryption certificate is uploaded.
The issue that might occur is that the outgoing email to the sender of the s/mime signed email does not get encrypted.
Symantec Corporation is committed to product quality and satisfied customers. This issue is currently being considered by Symantec Corporation to be addressed in a forthcoming version or Maintenance Pack of the product. Please be sure to refer back to this document periodically as any changes to the status of the issue will be reflected here.
A workaround is to manually import the x.509 encryption certificate as an external user.
Symantec Encryption Desktop