Microsoft Exchange 2007 & 2010 Maximum Databases

For Exchange 2007 Standard Edition a mailbox server can only hold 5 databases (public folder or mailbox).

For Exchange 2007 Enterprise Edition a mailbox server can hold 50 databases (public folder or mailbox).

For Exchange 2010 Standard Edition a mailbox server can only hold 5 databases (public folder or mailbox).

For Exchange 2010 Enterprise Edition a mailbox server can hold 100 databases (public folder or mailbox).