SBS 2008: No Exchange mailbox created for new users

Mailboxs are not created for new users created in SBS 2008,
Error in log (C:\Program Files\Windows Small Business Server\Logs\AddUser.log)

[8120] 090515.192332.7283: Messaging: MessagingTaskException: Unable to find default mailbox database with name [Mailbox Database] – Check access and verify if mailbox database exists – Error# (80004)

[8120] 090515.192332.7595: AdminTME: Status: TaskId = MessagingTasks.TaskCreateMailbox, RootTaskId = TaskCreateUser, Success: True, Warning: True, Continue: True, Message: Unable to find default mailbox database. Make sure mailbox database exists and you have access to view the database.

Resolution

1. Open the Exchange Management Console
2. Expand Server Configuration and select Mailbox
3. Open the Mailbox Database Properties of the First Storage Group in the Database Management tab
4. On the General tab, ensure that the name of the database is Mailbox Database
   

Source: TechNet