Starting in Exchange Server 2003 SP2, the database size for your Exchange Store can now reach 75 Gigabytes. By default, Exchange Server 2003 has a default database size of 16gigs, and when you reach that limit, Exchange will finish its transactions and dismount the store. If your default store size was 16gigs and you installed Exchange 2003 SP2 and wonder why you are having these types of problems, this is because Microsoft will only increase the default store size to 18gigs. As this might sound silly, it does make perfect sense. If Microsoft automatically increased the store size to 75 gigs, it would be easy to overlook what size your store is and you could use up all the space on your hard drive.