When you're on Zune.net, you can send and receive messages from your friends right from your inbox.
As long as you're connected to the Internet, you can also check your Zune.net inbox to see what's in your device inbox—songs, pictures, podcasts—since the last time you synced with your computer. You can even play 30-second clips from songs that have been sent to your Zune.net inbox, although to play entire songs or podcasts or view pictures, you need to open them in the Zune software.
If a song isn't available on Zune.net or at Zune Marketplace—a home recording, for example—you'll see any song details listed with the song, but it will be marked as not available.
You can do several things from your Zune.net inbox.
Open your inbox on Zune.net
Download a song on your wishlist
View a sender's Zune profile
Block messages from someone