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How to Export Exchange Online Mailbox Size Report in Microsoft 365

Are some of your Exchange Online users encountering problems while trying to send or receive emails in their mailboxes? Have you verified if they're dealing with the 'Mailbox Quota Exceeded' error? If you're yet to pinpoint these mailboxes, you can employ the following methods to effectively manage the Microsoft 365 mailbox size quota to avoid being exceeded.

Native Solution

Microsoft 365 Permission Required


Global Admin or Exchange Admin.

Option 1 Using Microsoft 365 Admin Center

  • Under Reports, open Usage»Exchange»Mailbox usage that shows the Office 365 mailbox size report with overall mailbox usage.
  • Now, you can verify the storage quota for all the Exchange Online mailboxes along with the quota status, prohibit send/receive quota, etc.
  • Use the export option to download the report in CSV format.
Using Microsoft 365 Admin Center

Option 2 Using Windows PowerShell

  • Run the below cmdlets to list the Exchange Online mailboxes quota with their storage size limits.
  • Windows PowerShell Windows PowerShell
    Get-Mailbox | ForEach-Object { $mailboxStats = Get-MailboxStatistics -Identity $_.UserPrincipalName; [PSCustomObject]@{ DisplayName = $_.DisplayName; TotalItemSize = $mailboxStats.TotalItemSize; IssueWarningQuota = $_.IssueWarningQuota; ProhibitSendQuota = $_.ProhibitSendQuota; ProhibitSendReceiveQuota = $_.ProhibitSendReceiveQuota} } 
  • The above cmdlet lists all the mailboxes with their size properties such as TotalItemSize ProhibitSendReceiveQuota ProhibitSendQuota and IssueWarningQuota.
  • Use the export cmdlet to download the Exchange Online mailbox quota of Microsoft 365 users.

Option 3 Using PowerShell Script

  • Since there is no way to get all the Exchange mailboxes’ details with a single cmdlet, we have prepared a PowerShell script to retrieve the exact details efficiently.
  • Download and run the following script in the Administrator PowerShell.
Using PowerShell Script
AdminDroid Solution
More than 150 reports are under free edition.

AdminDroid Permission Required

Any user with report access delegated by the Super Admin.

Option 1Using AdminDroid

  • Open the AdminDroid Office 365 portal.
  • Navigate to Reports»Exchange»Mailbox Settings»Mailbox Quota.
  • By using the download button, you can export the report in any format such as CSV, XML, HTML, etc.
Using AdminDroid

Get the entire list of user mailboxes with mailbox size, prohibit send quota, prohibit send receive quota, etc.

You can also use the custom-made report only for mailboxes over the warning storage quota.

Option 2Using AdminDroid

  • Navigate to the Mailboxes Over Warning Quota report resided under Reports»Exchange»Mailbox Usage.
Using AdminDroid

Get Office 365 mailbox size, mailbox used percentage, issue warning quota, prohibit send quota, etc. of mailboxes over the warning storage quota.

  • Experience enhanced insights and visualizations. Explore bird's eye view with built-in charts for effortless mailbox storage quota analysis.

Simple yet the best! Isn't it?

Don't let Exchange Online users' mailbox storage slip your attention - Transform mailbox storage quota management to the next level with AdminDroid.

Witness the report in action using the

Exchange OnlineCheck the Exchange Online Mailbox Quota to Manage the Storage Usage in Microsoft 365

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What happens when the Exchange Online mailbox is full?

When the Exchange Online mailbox is full, it rejects any incoming mail and sends a non-delivery report (NDR) to the sender. Also, you experience the following issues if your mailbox storage quota is exceeded.

  • Bounced emails Incoming emails bounce back to the sender, indicating that 'Delivery has failed to these recipients or groups'.
  • Email inconsistencies across devices If your mailbox is full, it can result in synchronization problems between multiple devices. This can cause inconsistencies in email status and prevent changes from being reflected across all devices.
  • Email loss Emails may be rejected if your account's storage limit is reached, requiring senders to resend them when space becomes available.

By proactively managing your mailbox size, you can prevent these issues and maintain uninterrupted email communication.

AdminDroid offers a convenient solution for efficiently tracking undelivered emails in Exchange Online mailboxes.

  • Simply access the dedicated undelivered emails report found under Audit»Email»Email Activities.
  • This report exclusively provides detailed information on undelivered emails, sender address, recipient email, received time, etc. You can also utilize the subject column to view the subject of each undelivered email.

How to configure storage quotas for a mailbox in Office 365?

The size limit of an Exchange Online mailbox depends on your Microsoft 365 plan. By default, the mailbox limits in Microsoft 365 include a warning limit of 98% of the mailbox capacity, a send limit of 99% of the mailbox capacity, and a send/receive limit of 100% of the mailbox capacity.

Admins can configure and adjust the storage quota settings for user mailboxes to ensure sufficient storage capacity is allocated.

The Exchange admin center (EAC) cannot configure storage quotas, even though it is mentioned in Microsoft's support documentation that the EAC can be used to do the operation

However, if you are an Exchange Online admin who needs to configure storage quotas, We recommend you use PowerShell to configure storage quotas.

  • Connect to your Exchange Online module using the required cmdlets.
  • How to set the issue warning quota for a mailbox?
    To set the Issue warning quota, use the below cmdlet
    Set-Mailbox -Identity <identity> -IssueWarningQuota <value>
  • How to set the ProhibitSendQuota for a mailbox?
    To set the prohibit send quota, use the below cmdlet 
    Set-Mailbox -Identity <identity> -ProhibitSendQuota <value>
  • How to set the ProhibitSendReceiveQuota for a mailbox?
    To set the prohibit send receive quota, use the below cmdlet
    Set-Mailbox -Identity <identity> -ProhibitSendReceiveQuota <value>
  • How to check the Office 365 mailbox size limit in PowerShell?
    To get the mailbox size and quota using PowerShell
    Get-Mailbox <Identity> | Format-List IssueWarningQuota, ProhibitSendQuota, ProhibitSendReceiveQuota

*Replace <Identity> with the name, email address or alias of the mailbox. And set value for IssueWarningQuota, ProhibitSendQuota and ProhibitSendReceiveQuota. The value range for any of the storage quota settings is from 0 through 2047 gigabytes (GB).

You may also combine the parameters in a single cmdlet and execute.

By using AdminDroid’s Schedule Reports, administrators can proactively monitor and manage user mailbox quotas effectively.

  • Navigate to Schedule Reports in your AdminDroid portal.
  • Search and select the Mailbox Quota report from the reports.
  • Set the frequency for the schedule and add recipients to get the reports emailed.

The Mailbox Quota report is now set to receive regular updates based on frequency, providing the latest information on users' mailbox quotas.

Why there is a 'Mailbox is full' warning message for a mailbox that hasn't reached the storage limit?

This issue occurs if the outlook mailbox size exceeds the mailbox quota. It's important to note that the size displayed to the user does not account for the Recoverable Items folder. The folder which contains deleted items and other recoverable data, is not visible to users.

As a result, the displayed Exchange Online mailbox quota may not accurately reflect the true size, including the content within the Recoverable Items folder. To recover from this issue, verify the storage quotas of the user's mailbox and run the following cmdlet.

Get-MailboxStatistics | fl StorageLimitStatus, TotalItemSize, TotalDeletedItemSize
  • If the StorageLimitStatus value is not empty, it indicates that the mailbox has exceeded its quota.
  • The TotalItemSize value represents the mailbox size visible to the user.
  • The TotalDeletedItemSize value represents the size of the Recoverable Items folder, which remains hidden from the user's view.

If the TotalItemSize value surpasses the ProhibitSendReceiveQuota value, or if the TotalDeletedItemSize value exceeds the RecoverableItemsQuota value, consider deleting items from the mailbox.

  • AdminDroid can assist you in monitoring your users' mailbox quotas daily. It proves to be a valuable tool in managing and tracking mailbox storage effectively.

Recoverable Items Managed Right: Keeping Your Office 365 Mailbox Size Tight!

AdminDroid also offers the ability to track the recoverable storage quota, including the recoverable items quota and recoverable items warning quota.

  • To check the recoverable items quota of your users, you can just use the columns Recoverable items quota and Recoverable items warning quota in all Exchange Online mailbox reports.

When should I use Archive and Online Archive mailbox in Exchange Online?

  • Archive Mailbox You can archive user mailboxes to preserve older emails and to have extra storage space for archiving older emails, keeping their primary mailbox clutter-free. By utilizing the archive mailbox, users can manage the size of their primary mailbox by transferring less frequently accessed older emails, reducing storage consumption.
  • Online Archive Mailbox It is primarily designed for organizations that need to retain large amounts of data for a longer period, such as for compliance or legal requirements. Moving large amounts of data to the Online Archive mailbox helps reduce the size and performance impact on the primary mailbox.

AdminDroid: Streamlining In-Place Archive Mailbox Management with Comprehensive Reporting

AdminDroid can generate detailed reports on In-place archive mailboxes, displaying key information including archive mailbox size, archive quota, archive warning quota, etc. It provides an efficient solution for managing archive mailboxes effectively.

How to monitor mailboxes over the size quota in Exchange Online?

Mailbox exceeding the size quota is crucial in effective Exchange Online management. You can get the mailbox and its storage used from Microsoft 365 in the below ways:

  • Microsoft 365 Admin Center Navigate to Mailbox usage resided under Reports»Exchange. By using the storage used column, you can check users’ mailboxes individually from the list.
  • Exchange Admin Center To check mailbox size in the Exchange admin center, navigate to the Recipients»Mailboxes section. You can individually select the users and check the Mailbox Usage section, which provides information about their mailbox storage used.
  • Microsoft PowerShell Run the PowerShell script provided and get the detailed list of mailboxes with their storage quota details.

However, the Microsoft 365 admin center and Exchange admin center requires manual searching of mailboxes and PowerShell does not offer an easy way to find and manage the mailbox over the size quota.

AdminDroid: Streamlining mailbox monitoring over warning quota, simplifying the search.

Use the dedicated Mailbox Over Warning Quota resided under Reports»Exchange»Mailbox Usage to list the mailboxes which are over the warning quota.

We recommend utilizing the Quick Schedule feature which periodically sends the report to your inbox. Follow these steps to activate the quick scheduler option.

  • Click on Show Advanced options in the Quick Schedule option
  • By the Customize the email option, you can schedule the reports to be emailed only when the report data satisfies the condition, thus achieving the alerting experience using schedulers too.
  • You can also see the overview of created schedulers by navigating to the Schedule Reports page in your AdminDroid portal.

How to increase Office 365 mailbox size from 50 GB to 100GB?

When the mailbox size exceeds 50 GB, organizations are left with two choices that they can upgrade their Office 365 subscription or remove data from the mailbox. However, it is important to recognize that deleting data may not always be a straightforward or preferred solution.

  • To increase the storage space of user mailboxes, the simplest method is to upgrade from a Business subscription plan to an Enterprise plan.

Note: Business Basic and Business Standard plans to offer a mailbox storage limit of 50 GB. Upgrading to Enterprise E1, E3, or E5 plans will double the storage capacity to 100 GB automatically.

  • Or enable Exchange Online Archiving, which can provide additional storage space of either 50 GB or nearly unlimited space. With the 'Auto-expanding archive' feature in Microsoft 365, automate the process of moving older items to the archive.
To enable an Auto-expanding archive for a mailbox, run the following cmdlet after connecting to the Exchange Online module.

-Enable-Mailbox <user mailbox> -AutoExpandingArchive

AdminDroid: Simplifying Mailbox Archive Settings with Detailed Reporting

With AdminDroid, it's effortless to identify users with auto-expanding archive mailboxes. The user-friendly interface and pre-configured reports make it simple to identify the archive status of mailboxes, streamlining your mailbox management tasks.

How to manage the Exchange Online mailbox size?

Proper management of Exchange Online mailbox size is a key to efficient mailbox operations. To keep your mailbox size under control, consider the following:

  • Archive older items Move old items to a separate Outlook Data File for storage or use automatic/manual archiving to manage items effectively.
  • Empty the deleted items folder Regularly clear out the Deleted Items folder to free up space and remove unnecessary messages.
  • Empty the junk email folder Periodically clean out the Junk Email folder to optimize your inbox space for important messages.
  • Store attachments externally Save attachments outside your mailbox by utilizing team sites, OneDrive, or local folders on your computer. This helps prevent excessive space usage within your mailbox.

By following these practices, you can efficiently manage your mailbox size, optimize storage usage, and ensure smooth management within the constraints of Exchange Online storage quota.

  • AdminDroid can also report on storage occupied by the Exchange Online mailboxes over time with a dedicated report which gives valuable insights into mailbox usage over time.
  • You can monitor the Exchange Online mailbox storage used on a specific date. Efficiently monitor your users' storage consumption daily.

AdminDroid Exchange Online ReporterSimplifying the task of monitoring and managing Exchange Online mailbox sizes!

AdminDroid Exchange reporting tool stands as an all-inclusive solution for Microsoft 365 admins, empowering seamless identification and management of Exchange Online mailbox size quota without the necessity of intricate PowerShell scripts.

AdminDroid simplifies mailbox quota management by offering an efficient solution for users:

The Mailbox Quota report under Reports»Exchange»Mailbox Settings will provide you with detailed information on mailbox size, prohibit send quota, prohibit send receive quota, etc.

A Quick Summary

Gain a Centralized and Comprehensive View of Mailbox Sizes

Effortlessly locate all Exchange Online mailboxes with their respective sizes, consolidated in a single and accessible location.

Optimize Storage Allocation for Enhanced Efficiency

Swiftly manage mailboxes over the size quota and allocate storage resources optimally with the help of detailed reports on mailboxes.

Efficient Solution for Tracking Undelivered Emails

Access the dedicated undelivered emails report for detailed information on Microsoft 365 undelivered emails, including the subject, sender address, recipient email, and received time.

Access Detailed Information on Archived Mailboxes

Gain insights into the total number of archived mailboxes, their size, and the percentage of storage occupied.

Generate Reports Automatically for a Streamlined Process

Schedule and export Exchange Online mailbox sizes to csv, delivered directly to your inbox, providing constant updates on Office 365 mailbox quota.

Implement a Sophisticated Alert System

Create an alert policy to track daily mailbox storage and promptly address quota-related issues for efficient storage management.

Overall, AdminDroid monitors Microsoft 365 mailboxes by seamlessly enabling the tracking and management of mailbox sizes, providing uninterrupted control in managing your Exchange Online. Effectively prevent storage issues and manage mailbox sizes in your Microsoft 365 environment. Gain detailed insights, track changes, and optimize storage allocation with the help of AdminDroid.

Kickstart Your Journey with AdminDroid

Your Microsoft 365 Companion with Enormous Reporting Capabilities!

Common Errors and Resolution Steps for Mailbox Over Storage Quota

The following are possible errors and troubleshooting hints while dealing with mailboxes over the storage quota in Microsoft Exchange Online.

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

This error occurs when the mailbox ‘Prohibit Send Quota’ is achieved.

Troubleshooting hint :To resolve this error, you can increase the Prohibit send quota.

Set-Mailbox <UserId> -ProhibitSendQuota <Value>

Error: Your mailbox is 100% full. You can no longer send or receive messages.

This error occurs when the user Exchange Online mailbox storage is full.

Troubleshooting hint :To resolve this error, you can increase Microsoft 365 mailbox size for prohibit send receive parameters.

Error: Your mailbox has reached XMB, which is over 90% of your YMB quota. Please delete some messages to avoid exceeding your quota.

This error occurs when your Exchange Online storage is over the Issue Warning Quota.

Troubleshooting hint :You can increase the issue warning quota to resolve the error or increase your mailbox size.

Set-Mailbox <UserId> -IssueWarningQuota <Value>

Error: Mailbox Quota exceeded.

This error indicates that the allocated storage limit for the user mailbox has been surpassed.

Troubleshooting hint :To resolve this error, archive older items and empty the deleted items folder to remove unnecessary messages.

Error: Mailbox size limit exceeded.

This error indicates that a user's mailbox in Microsoft 365 has exceeded the allocated storage capacity that was assigned.

Troubleshooting hint :To resolve this error, review Exchange Online mailbox usage. Archive or delete unwanted items.