Getting Mailbox Statistics in Exchange 2007

The most basic Exchange Management Shell cmdlet to use is the Get-MailboxStatistics cmdlet on its own. Figure 1 shows a sample of the output of running this cmdlet with no additional parameters. This runs against the local mailbox server.

Figure 1: Default Results of Get-MailboxStatistics

As you can see, by default this gives us 4 pieces of information for each mailbox on the local server, namely the display name of the mailbox, the number of items in the mailbox, the mailbox storage limit status and the last logon time. The actual size of the mailbox is not shown by default so the first task is to determine the name of the attribute that stores this value. One way to determine the available attributes that can be retrieved is to pipe the results of the cmdlet into the Format-List cmdlet, or fl for short. For example, our cmdlet now becomes:

Get-MailboxStatistics | fl

Figure 2 shows the results of doing this, where the attributes of User2’s mailbox are shown.

Figure 2: Results of Get-MailboxStatistics | fl

Now you can see other important pieces of information, such as the TotalItemSize attribute that has a value of 1584504B, or approximately 1.5MB. Clearly User2 is not a big user of Exchange 2007. Now that we know the attribute that we are interested in is called TotalItemSize, we can modify our original cmdlet to extract this information along with the mailbox name and item count. The cmdlet to use is shown below. Note the fact that this time, we’ve used the Format-Table cmdlet, or ft for short, to produce the output in table format:

Get-MailboxStatistics | ft DisplayName,TotalItemSize,ItemCount

The result of this cmdlet is shown in Figure 3.

Figure 3: Get-MailboxStatistics With Mailbox Sizes

Now we are getting somewhere, as this is a fairly concise output telling us pretty much what we need to know. However, there are a couple of drawbacks to this output. Firstly, the output is not in ascending or descending order, so it is difficult to see quickly which mailboxes are the biggest. Also, the TotalItemSize column is shown in bytes by default which also does not make for easy reading.

Additional Get-MailboxStatistics Formatting

Let’s address the order of the output first. Sorting objects using PowerShell is really easy via the, you guessed it, Sort-Object cmdlet. All you really need to do for this exercise is to get the mailbox statistics and then pipe the results into the Sort-Object cmdlet before piping these results into the Format-Table cmdlet. For the Sort-Object cmdlet, all we really need to decide is which column you want to sort on and the direction you want to sort in. The first parameter we need to add to Sort-Object is the column name to sort on, which in our case is TotalItemSize. We then add either –Descending or –Ascending to give us the direction to sort in. Let’s show the largest mailboxes first, which is typically what administrators need to know. The cmdlet now becomes:

Get-MailboxStatistics | Sort-Object TotalItemSize –Descending | ft DisplayName,TotalItemSize,ItemCount

The result of this cmdlet is shown in Figure 4.

Figure 4: Get-MailboxStatistics With Mailbox Sizes in Descending Size Order

Next we need to convert the mailbox sizes from bytes into something more useful. Megabytes is the obvious answer although with the ever increasing mailbox sizes it will not be long before gigabytes will be used as the default. However, since on my test system I have only got relatively small mailbox sizes, I am going to display the mailbox sizes in kilobytes. To do this, we need to replace the TotalItemSize parameter in our cmdlet with something inherently more complicated:

@{ expression={$_.TotalItemSize.Value.ToKB()}}

So our cmdlet now looks like this:

Get-MailboxStatistics | Sort-Object TotalItemSize –Descending | ft DisplayName,@{ expression={$_.TotalItemSize.Value.ToKB()}},ItemCount

The result of this cmdlet is shown in Figure 5 below. If you want to display the mailbox sizes in MB, use TotalItemSize.Value.ToMB in the cmdlet above. Or you can use TotalItemSize.Value.ToGB of course.

Figure 5: Get-MailboxStatistics With Mailbox Sizes in KB

That’s looking much better. But wait! Look at the column names now. We can see that the column that was previously called TotalItemSize is now referenced in the rather cumbersome form of $_.TotalItemSize.Value.ToKB(). We can address that very easily by adding a new label to the cmdlet. In fact, all you need to do is to add a change to the cmdlet to re-label the column appropriately. The new cmdlet is shown below:

Get-MailboxStatistics | Sort-Object TotalItemSize -Descending | ft DisplayName,@{label="TotalItemSize(KB)";expression={$_.TotalItemSize.Value.ToKB()}},ItemCount

The result of this is shown in Figure 6:

Figure 6: Get-MailboxStatistics With Labeled Column Names

At last we have a useful output that is nicely formatted and one that we can use to identify the largest mailboxes. What you don’t want to be doing is running this script manually every day, week or month. Obviously applications such as System Center Operations Manager (SCOM) 2007 bring this information back to you via the management console, so how can we do a similar thing with the Exchange Management Shell? The most obvious method is to send the information via email so let’s look at how this can be done.