A Question of Quotas in Exchange Server 2010 (Part 1)

If you would like to be read the next part in this article series please go to A Question of Quotas in Exchange Server 2010 (Part 2).


In this article I want to look at mailbox quotas in Exchange Server 2010, specifically covering why they are important to the initial sizing performed during an Exchange Server 2010 design and then moving on to look at operational considerations. Many years ago mailbox storage quotas were a very important aspect to consider since disk space wasn’t cheap and mailbox sizes were often of the order of a few hundred megabytes in size, or even smaller in some cases. However, implementing mailbox storage quotas is still a very important consideration today as we shall see, even if mailboxes in the multi-gigabyte size range are the norm.

Mailbox Quotas and Sizing

One of the numerous key decisions you make when sizing an Exchange Server infrastructure is to determine the mailbox size that you will allocate to your users. This is performed in the Exchange Mailbox Role Calculator and an example is shown in Figure 1-1 where you can see that a 1GB mailbox is being sized for 1000 users. The mailbox size is used with other sizing parameters to determine, amongst other things, how much storage your solution will require. Allowing users to exceed their mailbox storage quotas may well lead to bigger issues later, such as disk space exhaustion on the partition housing the mailbox database.

Figure 1-1: Sizing an Exchange 2010 Infrastructure for 1GB Mailboxes

Mailbox Quotas Per Database

To ensure that users do not exceed the specified mailbox size that was used to size the overall system, we can set mailbox storage quotas. Mailbox storage quotas can be set on the properties of a mailbox database such that the quota applies to all mailboxes housed on the particular mailbox database. This can be seen in Figure 1-2 and here we can see the database properties as viewed in the Exchange Management Console.

Figure 1-2: Mailbox Storage Quotas – Per Mailbox Database via Exchange Management Console

You can configure the system to send the user an initial warning message at a particular mailbox size. You can also configure the ability to prevent users from sending new messages, as well as also receiving new messages, at a particular mailbox size. Also of interest in Figure 1-2 is the warning message interval setting, which is set to 1am by default. This is the time of day that Exchange sends the actual quota messages to the users. You may want to consider changing this value if, for example, you’d prefer to see the quota message nearer the top of the users’ inboxes when they next access their mailboxes in the morning. In such a scenario, you might consider changing the warning schedule to 7am or a similar time. Of course, that may not be desirable if you are operating a 24×7 environment where users are accessing their mailboxes at all times of the day and night. In those situations, some organizations may prefer to send multiple warning messages per day and this can be configured via the warning message interval setting.

As well as using the Exchange Management Console, it is also possible to use the Exchange Management Shell to view the mailbox storage quotas as you can see in Figure 1-3. Here we can see that the parameters of interest are the IssueWarningQuota, ProhibitSendQuota and ProhibitSendReceiveQuota parameters; these directly match to the options you can see in the Exchange Management Console in Figure 1-2. The Exchange Management Shell parameter that matches the warning message interval seen in the Exchange Management Console is QuotaNotificationSchedule. As you might expect, all of these values can be altered by using the Set-MailboxDatabase cmdlet with the relevant parameters.

Figure 1-3: Mailbox Storage Quotas – Per Mailbox Database via Exchange Management Shell

You might have noticed from Figure 1-2 and Figure 1-3 that the mailbox storage quotas shown are the default quotas set after Exchange Server 2010 has been installed. As you can see, users are given 2GB mailbox storage quotas by default. This means that it is very important to ensure that you reconfigure the mailbox storage quotas after the installation of Exchange Server 2010 unless, of course, you plan on giving your users the exact same mailbox storage quotas that you see in Figure 1-2. Giving your users larger quotas than you originally planned in the Exchange Mailbox Role Calculator could mean your mailbox databases becoming much larger than planned. As always, monitoring your system is a crucial activity.

Mailbox Quotas Per User

Setting mailbox storage quotas on the properties of a mailbox database is a very efficient way of ensuring that mailbox storage quotas can be assigned to many users at once and certainly cuts down on the administrative overhead. However, there will typically be occasions where you will need to configure mailbox storage quotas on a per-user basis and this can be achieved via the Exchange Management Console or the Exchange Management Shell. For example, in the Exchange Management Console you can access the properties of a user’s mailbox and navigate to the Mailbox Settings tab. From here, double-click the Storage Quotas option and you’ll be presented with a window similar to the one shown in Figure 1-4. This window is largely the same as the one you saw in Figure 1-2 but allows you to configure mailbox storage quotas on a per-mailbox basis by overriding the Use mailbox database defaults setting.

Figure 1-4: Mailbox Storage Quotas – Per Mailbox via Exchange Management Console

The same Exchange Management Shell mailbox quota parameters that we saw for a mailbox database earlier in Figure 1-3 are also available for an individual mailbox as you can see in Figure 1-5. The exception is the QuotaNotificationSchedule parameter since this is controlled at the mailbox database level rather than at the individual mailbox level.

Figure 1-5: Mailbox Storage Quotas – Per Mailbox via Exchange Management Shell

Mailbox Quota Messages

Now that we have seen how we set the quota settings at a mailbox database and at an individual mailbox level, let’s now have a look at the various messages that a user receives as a result of mailbox storage quotas. First, we’ll assume that a specific mailbox has the following quotas defined:

  • Issue warning at 10MB
  • Prohibit send at 12MB
  • Prohibit send and receive at 15MB

Of course, these quotas are really low purely for demonstration purposes in my lab environment. For the mailbox with these settings, the user will receive the message shown in Figure 1-6 when their mailbox exceeds 10MB in size and they are using the Outlook Web App (OWA) client. Notice that the message is sent with high importance. Also, you might be wondering what happens if a user has the prohibit send and receive mailbox quota set, their mailbox is full, and a new warning message is triggered for that user. In this case, the message is still delivered to the mailbox because these types of system message are excluded from any mailbox quotas.

Figure 1-6: “Mailbox Almost Full” Default Message


That completes part one of our look at mailbox quotas in Exchange Server 2010, where we have covered topics on sizing, configuration and what the end user actually sees in their mailbox when the warning message is issued. In part two, we’ll look at quota message characteristics, creating custom message text, mailbox quotas for archive mailboxes and finally diagnostics logging in relation to mailbox quotas.

If you would like to be read the next part in this article series please go to A Question of Quotas in Exchange Server 2010 (Part 2).

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