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Consider implementing storage quotas

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at https://go.microsoft.com/fwlink/?linkid=34707.]  

Topic Last Modified: 2010-07-27

The Microsoft Exchange Best Practices Analyzer Tool queries the Active Directory directory service to determine whether mailbox quotas have been set on each private message database (MDB) object. If the Analyzer tool finds that a particular private MDB contains more than 20 mailboxes and that quotas are not set on the MDB, Analyzer displays a Best Practice configuration message.

It is a best practice to apply quotas to all databases on computers that are running Exchange Server that host user mailboxes. The following are the limits that you should set at the database level. The limits are set on the Limits tab of the mailbox store properties page. Each limit is expressed in kilobytes (KB).

  • Warning   The Issue warning limit defines the mailbox size that triggers a warning e-mail message to the user. The warning message tells the user that the mailbox size is approaching the Prohibit send limit.

  • Prohibit send   The Prohibit send limit defines the mailbox size that prevents a user from sending e-mail. The user will receive an e-mail message from the Exchange server explaining that the mailbox size limit has been exceeded.

  • Prohibit send and receive   The Prohibit send and receive limit defines the mailbox size that prevents a user from both sending and receiving e-mail. All mail sent to the user is returned to the sender together with a non-delivery report (NDR).

As you set these rules, make sure that you provide a wide enough delta between the Prohibit send limit and the Prohibit send and receive limit. If the delta between the two limits is too small, the mailbox may reject messages before the user can clean-up the mailbox. Therefore, the best practice is to provide a buffer of at least 20 percent between the Prohibit send limit and the Prohibit send and receive limit. For example, if users are prohibited from sending new messages when their mailbox hits 100 MB, the Prohibit send and receive limit should be at least 120 MB.

To set mailbox limits on Exchange 2000 Server and Exchange Server 2003

  1. Open the Exchange System Manager.

  2. Locate the mailbox store displayed in the Analyzer tool regarding this issue.

  3. Right-click MailboxStore_Name and select Properties.

  4. Select the Limits tab.

  5. Modify the Issue warning at (KB), Prohibit send at (KB) limit and the Prohibit send and receive at (KB) limit.

  6. Click Apply, and then click OK.

To set mailbox limits on Exchange Server 2007 by using the Exchange Management Console

  1. Open the Exchange Management Console.

  2. Locate the mailbox store displayed in the Analyzer tool regarding this issue.

  3. Right-click MailboxStore_Name and select Properties.

  4. Select the Limits tab.

  5. Modify the Issue warning at (KB), Prohibit send at (KB) limit and the Prohibit send and receive at (KB) limit.

  6. Click Apply, and then click OK.

To set mailbox limits on Exchange Server 2007 by using the Exchange Management Shell

  1. The following example shows how to set the mailbox size at which a warning message is sent to the user. This attribute applies to all mailboxes in this mailbox database that do not have their own warning quota attribute set. You must specify either an integer or "unlimited." The default value is 1.9 gigabytes (GB).

    Set-MailboxDatabase "Mailbox Database Name" -IssueWarningQuota 1991680

  2. The following example shows how to set the mailbox size at which users associated with mailboxes in this mailbox database can no longer send messages. This attribute applies to all mailboxes in this mailbox database that do not have their own prohibit send quota attributes set. The limit value set must be either to an integer or to "unlimited".

    Set-MailboxDatabase "Mailbox Database Name" -ProhibitSendQuota 2097152

  3. The following example shows how to set the mailbox size at which the user associated with this mailbox can no longer send or receive messages. This attribute applies to all mailboxes in this mailbox database that do not have their own prohibit send receive quota attributes set. You must specify either an integer or "unlimited".

    Set-MailboxDatabase "Mailbox Database Name" -ProhibitSendReceiveQuota 2411520

For information about how to set mailbox limits in Exchange Server 2010, see Configure Storage Quotas for a Mailbox.

For more information about how to manage Exchange mailboxes in Exchange Server 2003, see Working with Exchange Server 2003 Stores.

For more information about how to manage Exchange mailbox limits in Exchange Server 2007, see How to Configure Database Limits and Properties.