The blog is getting lots of search engine hits for Exchange 2010 databases, probably because I wrote about the database size on the older versions in the past.
For older versions of Exchange see the posting here: http://blog.sembee.co.uk/post/Exchange-Database-Limits.aspx
For Exchange 2010, things are much the same.
On standard edition, the initial soft limit is 50gb, which can be increased as required. Enterprise edition has no limit configured.
To change the soft limit, you need to make a registry change and then restart the information store. The registry change is outlined in this article:
Note that the change is case sensitive.
If copying from the article, watch that it doesn't include an extra space at the end.
If you have the registry key set correctly, after restarting the information store, the following entry will be logged:
Log Name: Application
Source: MSExchangeIS Mailbox Store
Date: 29/07/2010 22:07:52
Event ID: 1216
Task Category: Storage Limits
The Exchange store Mailbox Database 1 is limited to 75 GB. The current physical size of this database (the .edb file) is <1 GB. If the physical size of this database minus its logical free space exceeds the limit of 75 GB, the database will be dismounted on a regular basis.
As with Exchange database since 2003 SP2, when the limit is reached, the database is dismounted. It can be remounted again immediately. However it will be dismounted at the next time the limit is checked, unless the registry has been changed and the information store service restarted.
The white space in the database continues to be taken in to account when the size is calculated - referred to as logical free space in this event log entry.