prize from sonos is a scam or real ?

It’s a scam

1. Sonos employees are duly marked in their Avatars and username descriptions.  Just adding “Admin” to your username isn’t enough.
2. No corporate giveaway is ever going to charge you shipping.  Ever.  It’s like giving you a free car and charging you for gas or floor mats.  Absurd notion.  
3. Gainsight is not fit for purpose.

See 

However, the email stating you received a private message is ‘real’, it’s just the private message contains spam content. It would likely help the moderators if you indicated from whom you received the private message.