This article describes how to add secondary email id for the Capture ATP Threat Reports on your My SonicWall account:
SonicWall Capture ATP offers:

2. On the Dashboard page, click on the My Account (circled with RED) and select My Personal Profile.

3. Under Settings | My Account section, click Manage Alternate Email.

4. Select the device you wish to add the alternate email id for and click on Add Alternate Email Address .

5. Add the Alternate Email Address in the text box and click on Save.

6. Now you Can see the updated Alternate Email ID on your end as below :

NOTE: The serial number used in the images is for testing purpose and is a free trial software.
NOTE: Please note that only the firewalls which are licensed for Capture ATP will be listed