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How to Export the Shared Mailbox Size Report in Microsoft 365

Shared mailboxes in Microsoft 365 are designed to facilitate collaborative email management from a centralized email address. While these mailboxes experience heavy traffic, the storage consumption can disrupt communication and lead to missed messages. Therefore, monitoring the size of Exchange Online shared mailboxes is essential. You can use the following methods to seamlessly obtain an Office 365 shared mailbox size report.

Native Solution

Microsoft 365 Permission Required

High

Global Admin or Exchange Admin.

Option 1 Using Microsoft 365 Admin Center

  • Login to the Microsoft 365 admin center.
  • Navigate to Reports»Usage»Exchange»Mailbox usage.
  • Add the Recipient Type column and sort it in ascending order to display the shared mailbox size limits and the storage usage at the top.
  • You can also add other columns like prohibit send/receive quota, issue warning quota, etc., to get all shared mailbox storage details.
  • Use the Export option to save the shared mailbox size report on your local machine.
Using Microsoft 365 Admin Center

Option 2 Using Windows PowerShell

  • Connect to the Exchange Online PowerShell module.
  • Execute the following command to list all shared mailboxes with their storage metrics, such as total item size, issue warning quota, prohibit send/receive quota, etc.
  • Windows PowerShell Windows PowerShell 
     Get-Mailbox -ResultSize Unlimited -RecipientTypeDetails SharedMailbox | ForEach-Object { $mailboxStats = Get-MailboxStatistics -Identity $_.UserPrincipalName; [PSCustomObject]@{ DisplayName = $_.DisplayName; TotalItemSize = $mailboxStats.TotalItemSize; IssueWarningQuota = $_.IssueWarningQuota; ProhibitSendQuota = $_.ProhibitSendQuota; ProhibitSendReceiveQuota = $_.ProhibitSendReceiveQuota} } | Format-Table
Using Windows PowerShell

Option 3 Using PowerShell Script

  • PowerShell scripting helps to export detailed storage data for all shared mailboxes for further analysis.
  • So, we’ve crafted a script that exports Exchange Online shared mailbox storage usage report in a more efficient and user-friendly manner.
  • Download and run the following script in the Administrator PowerShell.
GetSharedMailboxSizeReport.ps1
Using PowerShell Script
AdminDroid Solution
More than 150 reports are under the free edition.

AdminDroid Permission Required

Delegated

Any user with report access delegated by the Super Admin.

StepsUsing AdminDroid

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  • Login to the AdminDroid Office 365 reporter.
  • Navigate to the Mailbox Size Over Time report under Reports»Exchange»Shared Mailbox Info.
Using AdminDroid

This report helps to analyze the storage growth of Exchange Online shared mailboxes. Also, you can identify mailboxes that are nearing its full storage capacity with details like mailbox size, used percentage, item count, and size growth by daily usage.

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  • Customize the graphical representation chart to visualize the shared mailboxes that exceeded the storage quota.
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Optimize Shared Mailbox Storage Usage in Exchange Online!

Analyze shared mailbox size growth to mitigate disruptions in mail flow! Streamline Microsoft 365 shared mailboxes with AdminDroid.

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Exchange OnlineManage Shared Mailboxes Storage Usage in Microsoft 365

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What to do if a shared mailbox is full? What is the default limit of shared mailboxes in Exchange Online? How to increase the size of a shared mailbox? How to check shared mailbox usage in Microsoft 365? Can a user access the shared mailbox storage details? How to manage a large shared mailbox in Microsoft 365?

What to do if a shared mailbox is full?

If your shared mailbox is reaching its storage limit, take the following actions to maintain a smooth mail flow and prevent bounce-backs of incoming emails with non-delivery reports.

  • Find and delete outdated emails that are no longer required.
  • Consider implementing a retention policy to automatically delete emails after a specified period.
  • Clear unnecessary emails in the shared mailbox with large attachments.
  • Assign a license to a shared mailbox to increase its storage quota.
  • Consider archiving shared mailboxes to free up storage and manage them efficiently.

Archiving keeps the active mailbox cleaner and more efficient by moving older or less frequently accessed emails to a separate archive.

  • By utilizing AdminDroid’s Archived Shared Mailboxes report, you can effortlessly find the archive quota and archive warning quota for shared mailboxes.
archived-shared-mailboxes

ProTip: Schedule this report on a monthly, weekly, or daily frequency to closely monitor the archive quota storage stats for Exchange Online shared mailboxes.

What is the default limit of shared mailboxes in Exchange Online?

Refer to the following points to know the default storage limit of a shared mailbox in Microsoft 365.

  • Issue Warning Quota: If the shared mailbox is nearing its storage limit, members will receive a warning that the mailbox is approaching its storage quota. By default, the threshold is set to 49 GB.
  • Prohibit Send Quota: Once a shared mailbox reached its maximum storage limit (49.5 GB by default), delegated users are unable to send new emails. However, they can still receive new emails and access existing ones.
  • Prohibit Send or Receive Quota: If a shared mailbox limit is consumed fully (i.e., 50 GB), delegated users are unable to send, receive, or access emails in the mailbox.

However, these limits can be increased through licensing, archiving, or deletion of emails. Also, note that these shared mailbox storage quotas can be adjusted based on the organization's specific requirements and licensing arrangements.

How to increase the size of a shared mailbox?

By default, shared mailboxes in Exchange Online come with a storage of 50 GB. To increase the mailbox size from 50 GB to 100 GB, you will need at least the Exchange Online Plan 2 license.

How to assign a license to a shared mailbox in Office 365?

Assigning a license to a shared mailbox is similar to assigning a license to a user. You can do the following steps in the Microsoft 365 admin center.

  • Go to the Active users tab under the Users section and choose the appropriate shared mailbox from the list.
  • Navigate to the License and apps page and select the appropriate license. After that, click on Save changes.
assign-license

To assign a license to a shared mailbox using PowerShell, follow the steps below:

  • First, connect to the Microsoft Graph PowerShell and find the SKU ID of the licenses available in your Microsoft 365. 
    Connect-MgGraph -Scopes Directory.ReadWrite.All, User.ReadWrite.All
  • After that, execute the following cmdlet with the appropriate SKU ID and the UPN of the shared mailbox. 
    Set-MgUserLicense -UserId <Shared Mailbox UPN> -AddLicenses @{SkuId= "<SKU ID>"} -RemoveLicenses @()

How to check shared mailbox usage in Microsoft 365?

To obtain the storage usage of a specific shared mailbox, follow these steps using the Exchange admin center.

  • Login to the Exchange admin center and navigate to the Mailboxes tab under the Recipients section.
  • Select the shared mailbox from the list.
  • In the General tab, you can find the shared mailbox usage details, including total storage and the currently consumed percentage.

Schedule the Shared Mailbox Size Over Time report using AdminDroid!

  • Utilize the Schedule this report now option to monitor the shared mailbox storage periodically and get it delivered to your email.
customize-scheduling

Here's a handy tip: Utilize the Mailbox Display Name filter in the shared mailbox size over time report to track the storage trend of a particular shared mailbox.

Can a user access the shared mailbox storage details?

No, not every Microsoft 365 user can access a shared mailbox and utilize its storage. Only users with delegated permissions levels in Outlook shared mailboxes can access the storage, emails of a shared mailbox.


To access and view the shared mailbox storage details via the Outlook web, follow these straightforward steps:

  • First, open the shared mailbox in the Outlook web client.
  • Go to the View tab and choose the View settings option.
  • Then, navigate to the General tab and select the Storage option.
check-storage-in-outlook

Here, you can view the storage size details of the shared mailbox along with the percentage used. You can also get insights about the storage occupied by emails in the inbox, sent items, drafts, and deleted items.

While users with delegated access to a shared mailbox can access the mailbox and utilize its storage, it is imperative to frequently check the access rights permission.

In order to find all the Microsoft 365 users who have access rights to the Exchange Online shared mailboxes, we have a complete guide to export the shared mailbox permission report.

Here’s a snapshot of what the guide covers!

  • Using Microsoft 365 admin center: This section allows you to identify users who have read and manage permissions, send as permissions, and send on behalf of permissions for corresponding shared mailboxes.
  • Using Windows PowerShell: For more comprehensive results and to obtain shared mailbox permissions for all users, this section in our guide offers respective PowerShell cmdlets and a script.
  • Using AdminDroid: This section provides a shared mailbox permission report detailing the user's access rights. This report offers graphical, tabular, and combo views for quick visibility into delegate permissions. Additionally, it facilitates report export, advanced scheduling, etc.

Note: Furthermore, you can use the non-owner mailbox access report to audit whenever an Exchange Online mailbox is accessed by non-owners.

How to manage a large shared mailbox in Microsoft 365?

Microsoft 365 organizations can upgrade the shared mailbox subscription or remove data from the mailbox when it reaches the storage quota. As deleting emails is not a preferred or perfect solution, admins often choose to increase shared mailbox size in Office 365.

Assigning subscriptions like Exchange Online Plan 2, E1, E3, or E5 plans will double the shared mailbox storage capacity to 100 GB. However, even with the increased storage to 100 GB, it may not be sufficient for organizations with a more traffic.

In such a scenario, enabling the shared mailbox archive creates a separate archive mailbox with 50 GB of space. Moreover, with the auto-expanding archive feature in Microsoft 365, the archive mailbox storage can be increased up to 1.5 TB.

  • Use the following cmdlet in the Exchange Online PowerShell module to enable auto-expanding archives for a shared mailbox. 
    Enable-Mailbox <Shared Mailbox UPN> -AutoExpandingArchive
  • To enable auto-expanding archive in organization-wide, use the following command. 
    Set-OrganizationConfig -AutoExpandingArchive

Identifying archived mailboxes with auto-expanding archives is effortless with AdminDroid.

  • Examine the shared mailboxes with auto-expanding archives with the details, such as archive names, user principal names, auto-expanding archive status, etc.
  • Also, you can manage the shared mailbox storage by disabling archive for those that don't require high storage.
auto-expand-enabled-report

Handy Hint: You can use the Recipient Type Details easy filter to display only the shared mailboxes with an auto-expanding archive.

AdminDroid Exchange Online ReporterEfficiently level up your shared mailbox storage management!

The AdminDroid Exchange Online reporting tool provides comprehensive data to check shared mailbox usage with a thorough understanding. Serving as a one-stop shop, AdminDroid allows you to monitor shared mailbox storage, size growth statistics, email traffic, and more for optimal resource allocation!

AdminDroid's integral functionalities for shared mailbox size reports:

AdminDroid provides you with accurate insights and properties of the shared mailboxes available in Microsoft 365. The Mailbox Size over Time report helps to audit shared mailbox usage with insights detailing the used percentage, mailbox size, mail count, deleted mail count, and more for each day.

An Overview

Visualize Shared Mailbox Insights

Check shared mailbox storage details and gain clear insights through the Exchange Online dashboard with a quick glance for a bird's-eye view.

Regular Updates on Shared Mailbox Storage

Obtain real-time insights with the scheduling feature to get Exchange shared mailboxes info along with the storage insights to take necessary action and avoid quota limit exceeds.

Instant Alerts on Mailbox Peak Hours

Proactively monitor shared mailbox peak hours and days at which the maximum number of emails are sent and received using custom Microsoft 365 alert policies.

Inactive Shared Mailboxes in Microsoft 365

Utilize inactive shared mailbox reports to identify mailbox details, such as the last mail sent/received date and the number of inactive days.

Detailed Information on Mailbox Storage

Easily track Microsoft 365 mailbox storage quota and the current storage trends to address any Exchange Online mailbox size issues.

Shared Mailboxes with Litigation Hold

Identify the shared mailboxes with litigation holds that are capable of retaining deleted items and the original versions of modified items.

In summary, AdminDroid's Exchange Online management empowers you to effectively track, export, and manage shared mailbox storage, particularly by identifying mailboxes nearing capacity. Ultimately, this ensures optimal mail flow in shared mailboxes, minimizing disruptions and message loss.

Kickstart Your Journey with AdminDroid

Your Microsoft 365 Companion with Enormous Reporting Capabilities!

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Common Errors and Resolution Steps in Managing Shared Mailbox Storage Limits

Below are potential errors you may encounter and troubleshooting hints when dealing with shared mailbox storage issues.

Error: The sender's submission quota was exceeded.

This error occurs when you try to send more than 10,000 messages in the last 24 hours.

Troubleshooting hint :Wait for one day to send emails from the shared mailbox.

Error: Your mailbox is almost full.

This error occurs when your shared mailbox quota warning is reached.

Troubleshooting hint :To resolve this error, increase the shared mailbox storage through a license, or mail deletions. To temporarily bypass this error, change the issue warning quota using the following cmdlet. 

Set-Mailbox <Shared Mailbox UPN> -IssueWarningQuota <Size in KB>

Error: Your mail server's send quota has been exceeded. Please contact your mail admin or try re-sending from a different email account. Your email has been returned to your drafts folder.

This error occurs when your shared mailbox storage reaches the prohibited send quota.

Troubleshooting hint :To resolve this error, optimize the shared mailbox storage through a license, or mail deletions. To temporarily bypass this error, increase the prohibit send quota using the following cmdlet. 

Set-Mailbox <Shared Mailbox UPN> -ProhibitSendQuota <Size in KB>

Error: You've exceeded the storage limit for your mailbox. Delete some items from your mailbox.

This error signifies that the shared mailbox usage is full, and it has exceeded its assigned storage limit.

Troubleshooting hint :To address this issue, archive older items and clear the deleted items folder to remove unnecessary messages. Additionally, consider utilizing an auto-expanding archive for expandable storage and implementing a litigation hold to retain deleted mails.

Error: Get-MgSubscribedSku : Insufficient privileges to complete the operation

This error typically occurs when the user executing the cmdlet does not have the necessary permissions or appropriate scopes to perform the operation.

Troubleshooting hint :Connect to the Microsoft Graph PowerShell using the Directory.ReadWrite.All scope to ensure sufficient permissions for the operation.

Error: BootResult: accessDenied Back Filled Errors: Unhandled Rejection: Error: 500: undefined|undefined: undefined err: Microsoft.Exchange.Data.StoreObjects.AccessDeniedException

This error occurs when the user's access rights are not correctly configured or have been removed for the shared mailbox. It also occurs when permissions have been recently granted.

Troubleshooting hint :To resolve this, check the access rights of the user for the shared mailbox. If they are correctly configured, wait for some time and try opening the shared mailbox again.