Hi folks! For those of you that provide multi-tenant support there is good news on the Exchange front!
Exchange 2010 SP1 will have built-in multi-tenant support and SPLA users will no longer have to use MHMC 4.5 to host different companies in Exchange! Yay!
There are somethings that are not supported however such as public folders in Exchange 2010 multi-tenancy. You can read more details about this here.