Microsoft Exchange Server 2013 : Mailbox management - Setting mailbox quotas

Storage is much cheaper today than ever before. Therefore, it is has become feasible to provide large mailboxes on a very economical basis. As storage prices continue to drop, the tendency to contemplate larger mailbox sizes will also continue. Microsoft is looking at how servers and clients can manage 100-GB mailboxes, which is a huge amount of information when compared to the meager 25-MB mailboxes that were commonplace when Exchange 4.0 was launched in 1996.

Users expect that they will have large mailboxes at work, largely because consumer email systems continually increase the space they allow for free mailboxes. The question often asked is, if Gmail or Outlook.com can offer a huge amount of storage for email, why can’t my company’s email system do the same?

On a commercial level, the cloud-based versions of Exchange usually provide mailboxes of at least 25 GB, further confirming the user view that they should have the same storage available when at work. A proliferation of free storage repositories such as SkyDrive exist to offer users even more space.

A major engineering focus for Exchange over the last two versions has been how to enable users to keep as much information as possible in the Store rather than forcing users to keep moving data into PSTs, as they were forced to do in the past. Keeping everything in the Store is easier for users and makes it feasible for companies to operate a comprehensive compliance regime. Features such as archive mailboxes increase available storage even more, and retention policies allow unwanted information to be aged out and removed from mailboxes automatically.

Given the pressure for workers to be as productive as possible, it makes little sense to force users to spend time (sometimes on a daily basis) cleaning up mailboxes before they can process email. Time spent reviewing and deleting messages from a mailbox would be better spent dealing with more mission-critical business.

The result of these influences is that it is now common for administrators to set a reasonably large default quota and not worry too much more about the issue until users look for additional quota. Apart from letting administrators get on with more important work, the fact is that it takes even prolific users some time to fill a multi-gigabyte mailbox. Another approach often seen is that mailbox quota defaults are immediately set to higher values (usually 5 GB or higher) after a database is created so that any new mailbox created in the database receives a quota that should not need adjustment for a couple of years.

Even with these factors, the vast majority of users in large corporations probably still have a mailbox quota of less than 1 GB. The average mailbox size has been rising slowly. If you work for a company that still likes to exert some level of control over mailbox quotas, if only to calculate the storage requirements for databases with some degree of accuracy, you can set three mailbox properties that combine to control the quota available to the mailbox.

Exchange sends messages to warn users of approaching quota thresholds or to tell them that they have exceeded their mailbox quota according to a schedule maintained in the QuotaNotificationSchedule property that is set on every mailbox database. You can see the schedule for a database by running a command like this:

Get-MailboxDatabase –Identity 'DB2' | Format-List Name, QuotaNotificationSchedule

When a new mailbox is created, it inherits its quota settings from those assigned to the database in which it is created. For example, any mailbox created in the database shown in Figure 1 that is not assigned an individual set of quotas begins receiving warning messages at 1.9 GB, stops being able to send new messages at 2 GB (the mailbox quota), and cannot receive any more new mail at 2.3 GB. These are the default values Exchange 2013 assigns to new mailbox databases.

Figure 1. Viewing the default storage quotas for a mailbox database

Mailboxes that use the quotas inherited from the database settings have their UseDatabaseQuotaDefaults property set to $False, whereas those that have individual quota settings have the property set to $True. It’s therefore easy to find out which mailboxes in a database have been assigned individual quotas with a command like this:

Get-Mailbox –Database DB2 | Where-Object {$_.UseDatabaseQuotaDefaults –eq $False} | Format-Table DisplayName, IssueWarningQuota, ProhibitSendQuota, ProhibitSendReceiveQuota

If the default mailbox quotas Exchange 2013 sets don’t work for your installation, you need to update the properties of mailbox databases to set whatever values you want to use. After updating the databases, you might need to review mailboxes that already exist in each database to determine whether their quotas need to be adjusted.

At any time after they are created, individual mailboxes can be assigned specific quotas to meet their business needs. To update quotas with EAC, select the mailbox, view its properties, choose Mailbox Usage, and click More to reveal the fields in which you can input the new quota settings (Figure 2). Click Customize The Settings For This Mailbox to make the three quota fields active. Note that EAC does not allow you to enter values using more than two decimal places.

Figure 2. Setting quotas for an individual mailbox

You can also use the Set-Mailbox cmdlet to assign new quota values to mailboxes. For example:

Set-Mailbox –Identity 'Redmond, Tony' –UseDatabaseQuotaDefaults $False –IssueWarningQuota 500MB –ProhibitSendQuota 520MB –ProhibitSendReceiveQuota 540MB

Quota values can be expressed in KB, MB, or GB. A one-line EMS command is a great way to set the same quota on a group of mailboxes. For example, you could set the same quota values for every mailbox in an OU:

Get-Mailbox –OrganizationalUnit 'contoso.com/Exchange Users' | Set-Mailbox
–UseDatabaseQuotaDefaults $False –IssueWarningQuota 500MB
–ProhibitSendQuota 520MB –ProhibitSendReceiveQuota 540MB

You can use the same approach to assign quotas to every member of a distribution group. In this case, the command to give members of the IT department the quotas they deserve is:

Get-DistributionGroupMember –Identity 'IT Department' | Set-Mailbox
–UseDatabaseQuotaDefaults $False –IssueWarningQuota 985MB
–ProhibitSendQuota 1GB –ProhibitSendReceiveQuota 1.1GB

To check that the right quotas are in place, you can do something like this:

Get-Mailbox –Identity 'Redmond, Tony' | Select *quota*

Exchange maintains several other quota settings for mailboxes. The RecoverableItemsQuota and RecoverableItemsWarningQuota settings are roughly equivalent to the ProhibitSendQuota and IssueWarningQuota settings except that they control the amount of data that a mailbox can store in the Recoverable Items folder. By default, Exchange 2013 allows 30 GB of recoverable data to be held in a mailbox. The RulesQuota setting limits the amount of rules data a mailbox can hold, and 64 KB is the default. The ArchiveQuota and ArchiveWarningQuota settings control how much information can be held in an associated personal archive if this feature is enabled. Exchange allows an unlimited quota for the archive, so in this case, the quota has been set back to a hard limit of 50 GB (still more than enough).

New quotas are not immediately effective because the Store first has to refresh the cached data it holds about mailbox settings. The cache is refreshed every two hours, so you could have to wait this long before the new quota settings are in place. You can update the Reread Logon Quotas Interval registry setting to force more frequent refreshes of this data at the expense of additional system overhead. (Refreshing the data every five minutes would definitely be a bad idea; every hour or so should be acceptable.) The DWORD value is set in seconds. (The default value is 7,200 seconds, or two hours.) This value depends on other values that control how often Exchange retrieves information from Active Directory. Another option is to restart the Information Store process to force a cache refresh. This approach is acceptable on a test server but probably not on a production server.

(number of mailboxes * quota) = database size on disk

(number of mailboxes * quota) * 1.2 = database size on disk

Don’t forget to reserve some additional disk space to accommodate expected database growth over the next year or so and to account for temporary space required by activities such as mailbox moves or offline database maintenance.