Microsoft Exchange 2010 what affects the size of the mailbox database

The Microsoft Exchange database size depends mainly on the number and size of the mailboxes located at the mailbox database.

Size of boxes, which will be located in a given database, we can predict and control so that we know about what size will depend on our database.

Unfortunately, there is still a couple of other factors that could cause sudden expansion of the size of the database or its continued growth.
Below we will present on what you should look in the settings database.

The main parameter determining the maximum size of mailboxes in the database is Quota.
Quotas can be set at the mailbox database and then will apply to all mailboxes in the database if individual quota is set on mailbox.

The quotas can view the values and set in the Exchange Management Console in the properties of the database, we can also be changed using the PowerShell command:

Displays the current quota limits:

 Get-MailboxDatabase "MailboxDatabase" | Select *Quota*

Another important parameter is the retention time, which can be set to the database level or at the level of the mailbox.
We define here

• MailboxRetention – time that the mailbox will be retained afted disabled, by default, 30 days
• DeletedItemRetention - time after which messages deleted in mailbox will be deleted permanently, the default 14 days

Get-MailboxDatabase "MailboxDatabase" | fl *retention*

We must remember that mailbox and the deleted items will be removed permanently only when the full backup will be made for database. We can omit this condition by un-checking the “Do not Permanently delete items until the database has been backed up“, but it is not recommended.

In addition, each base has a specified Quta value for the deleted data – Recoverable Items.
In this case, default values are:

• RecoverableItemsQuota 30GB
• RecoverableItemsWarningQuota 20GB

It should be noted here that the value of this Quota is applied to each mailbox rather than the sum of mailboxes located at the database.

To display the value of this Quota, we need to use PowerShell:

Get-MailboxDatabase "MailboxDatabase" | FL recoverable*

In the event of a reduction RecoverableItemsQuota, if the limit of its value will be achieved by the mailbox, you will see information about the achievement of an acceptable size of the store for mailbox.

If you want to check the size of the deleted items for a given mailbox, type:

Get-MailboxFolderStatistics -Identity "John Smith" -FolderScope RecoverableItems | Format-Table Name,FolderPath,ItemsInFolder,FolderAndSubfolderSize

Conversely, if we are interested in the size of all elements that are removed in all mailboxes in a given database, we can write:

Get-Mailbox -Database "MailboxDatabase" | Get-MailboxStatistics | %{$_.TotalDeletedItemSize.Value.ToMB()} | Measure-Object -sum

Also, if we enable an audit for the mailboxes, can causing expansion of the database, because the audit records are placed in each mailbox store which is audited.
So when you turn the audit should be specified for how long you want to store audit entries (default 90 days) and what is relate to the audit.

Information on the audit for a given mailbox can be viewed using:

Get-Mailbox "John Smith" | fl *audit*

If for any mailbox you want to delete all Recoverable Items use the command:

Search-Mailbox -Identity "John Smith" -SearchDumpsterOnly -DeleteContent

To all of these mechanisms to work properly it is also important to set an appropriate time to perform the Maintenance for a given database.
Ideally, this was a time in which the database is the least used.