SystemMailbox {GUID} is offline? Will this prevent my transition to Exchange 2010?

I have a single forest. single domain with Exchange 2003 I'm trying to transition to Exchange 2010. I have three DCs in the domain.

I have run the following commands, all of which have completed successfully:

• setup /pl
• setup /ps
• setup /preparead
• setup /preparedomain

On all three DCs, I see the new Microsoft Exchange Security Groups in the root of the AD-Users and Computers MMC. However, on one of my three DCs, I have a folder (or is it an OU?) titled "Microsoft Exchange System Objects" that has an object titled"SystemMailbox {GUID}" which appears to be offline because it has a big, red X by it!

I have few basic questions:

1.) What is this object and should I be concerned about it?

2.) More importantly, is it anything I need to address before proceeding with my actual install of Exchange 2010 and starting the transition of mailboxes over to the new 2010 server, etc.?

Thank you,

Ed