Integrate Office 365 room mailbox with SharePoint

I'd like to add a room mailbox that is hosted on Office 365 to my internally hosted SharePoint 2010 site.

Here is what I've done so far:

• Created the room mailbox on Office 365
• Created a SharePoint site to hold the calendar
• Added an Outlook Calendar webpart

I keep getting: "Cannot import this Web Part."

For the server address, I tried a few options:

• m.outlook.com
• mail.office365.com
• [server where my mailbox is].outlook.com
• [server where my mailbox is].mailbox.outlook.com

All return the same error when I click ok.