Recomended Size of exchange database

In Exchange Enterprise edition there is no limit to the size of your databases. However, since you have the ability to create multiple databases, it is a good idea to create one for your management staff, and another for general staff. This separates the mailboxes, and also allows you to set different mailbox quotas for these different "types" of users.

-tigermatt

Gereally speaking, the speed of your backup and restore defines the top limit to the size of an information store.  The figure that is often quoted as the sweet spot beyond which you suffer extended backup/restore delays is 75GB, but it's really a question you need to answer for yourself once you've considered all the factors that are relevant to you.

If you go down the road of creating multiple databases (Enterprise version), then the current advice to to create a new storage group for each DB - this is because transaction logs are shared per storage group, not per database, and by keeping to one DB per storage group you maximise the seperation of your transaction logs, and thus simplify any DR scenario that needs you to reply transaction logs.

Hopefully I didn't offend anyone...
I think the question was about an official MS statement regarding the 50GB limit, which was posted on my first comment.