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Shared Mailbox Size – Office 365 Reports

Dec 21, 2012 by Emma Robinson

We’ve recently added a new report into our advanced Office 365 reporting software that shows you the sizes of all Unlicenced Shared Mailboxes in your Office 365 tenant. As you may know, Shared Mailboxes do not require an Exchange Licence in Office 365 as long as they are under 10GB in size. If they grow over that size, you need to apply a license to them or they stop working – or worse, get deleted!

Please Note! The maximum size limit for Office 365 Shared Mailboxes used to be 5GB. In September 2013 Microsoft increased this limit to 10GB.

Unlicenced Shared Mailbox Size Report

By default the report shows the above, which includes all Office 365 Shared and Room mailboxes that have no license assigned to them. We can use the powerful filters to return only those that are over 10GB in size.

Simply click the Report Filters button, and filter on Mailbox Size greater than 10737418240 (This is 10GB in Bytes).

Filter on Shared Mailboxes over 10GB

You’ll then get the results of this query.

Results of Filter

This is a good opportunity to click the Save Reports button in the Report Filters box to save this report for later. Next time you want to run the report you can just go to the Saved Reports section and run it without remembering what filters to apply.

Otherwise, you can click the Export Report report to save it as a CSV file or the Print Report button to print it out. If you are using a modern browser, you can use the print report function to save this to a PDF file.

What about shared mailbox growth over time?

You can use our existing Mailbox Sizes over Time report to track the growth of Shared Mailboxes over time.

Firstly, click the Mailbox Sizes over Time report and click Report Filters. Then filter for Recipient Types equal to either RoomMailbox or SharedMailbox.

Shared Mailbox Growth Report

And you’ll see how they’ve grown over time

Shared Mailbox Growth Report Results

Our example looks a bit strange because we artificially increased the size of one of our demo shared mailboxes for these new reports…

Do I have licenses assigned to Shared Mailboxes smaller than 10GB?

Whilst there are some reasons why you would want to assign a license to Office 365 Shared Mailboxes under 10GB, generally, you don’t require them.

You can use Cogmotive Reports to find out if you have any Licenced Office 365 Shared Mailboxes that are under 10GB in size. You might be able to remove the license from these mailboxes and save some money!

To do this, click on Custom Report and add the following fields:

  • Display Name
  • Login Name
  • Recipient Type
  • Office 365 Subscription
  • Mailbox Size

Then add two filters to return only SharedMailbox or RoomMailbox.

Custom Report to show licenses assigned to Shared Mailboxes

You can now see all the Office 365 Shared Mailboxes and their sizes in Bytes that exist in your Office 365 tenant with a license assigned. You can go through this list and see if any have a license assigned!

Exporting the Report Data

Most of our reports offer the ability to Export the data to CSV or PDF format.