HMC 4.5 - Not enough free mail storage to satisfy this request

Not sure where to ask this since the HMC 4.5 forum is archived.

We are running HMC 4.5 on an Exchange 2007 server. One of our organizations needs a new mailbox but when I try to add it I get the message: Not enough free mail storage to satisfy this request.

I have made sure that the Exchange Resources is expanded enough but it still won't let me add a mailbox. I was able to delete one mailbox to add this one but now I can't add any more. What .xml command do I need to run to expand the allocation for this particular organization?

Thanks,