Exchange Online

How to Find Mailboxes Over the Warning Quota in Exchange Online

Email is the heartbeat of modern business communication. But when an Exchange Online mailbox exceeds its warning quota, it can cause disruptions in mail flow. As the mailbox warning quota alert is sent only to the user and not to admins, it often goes unnoticed. Therefore, this guide shows how to find Exchange Online mailboxes that have exceeded their warning quota, so that admins can take action before the email flow is affected.

Check Mailboxes Exceeding Warning Quotas in Microsoft 365 Admin Center

Microsoft 365 Permission Required

Reports Reader Least Privilege

Global Admin Most Privilege

Log in to the Microsoft 365 admin center.
Navigate to Reports»Usage»Exchange»Mailbox usage.
Here, you can identify mailboxes that exceeded their warning quota by referring the Quota status column.
To quickly view mailboxes with a ‘Warning issued’ at the top, sort the Quota status column in descending order.
Use the Export option to download the report in CSV format.

Check Mailboxes Exceeding Warning Quotas in Microsoft 365 Admin Center

Track Mailboxes Over Warning Quota using PowerShell Script

Microsoft 365 Permission Required

Reports Reader Least Privilege

Global Admin Most Privilege

In the Microsoft 365 admin center, you can download the details like current mailbox size and the warning quota size. However, there is no option to filter mailboxes that have exceeded their warning quota.
Likewise, there's no direct PowerShell cmdlet to find mailboxes that have exceeded the mailbox warning quota.
To address this, we’ve developed a script that exports only the mailboxes that have exceeded their Issue warning quota.
Download and run the following script in PowerShell as shown below.
```
./GetMailboxUsageAndQuotaReport.ps1 -OverIssueWarningQuota
```

Track Mailboxes Over Warning Quota using PowerShell Script

GetMailboxUsageAndQuotaReport.ps1 The script retrieves all the user and shared mailboxes that exceed their warning quota. Additionally, it retrieves their warning quota, prohibit send quota, prohibit send and receive quota, and available storage.

Simple & Quick
Export Mailboxes Over Warning Quota Report Using AdminDroid

AdminDroid Permission Required Delegated

Any user with the report access delegated by the Super Admin.

Log in to the AdminDroid Microsoft 365 Reporter.
Navigate to the Mailbox Over Warning Quota report under Reports»Exchange»Mailbox Usage.
This report provides detailed insights into mailboxes that exceed their warning quota, along with details like used percentage, mailbox size, last logon time, mailbox type, and more.
Additionally, you can download the report in various formats such as CSV, HTML, and PDF.

Export Mailboxes Over Warning Quota Report Using AdminDroid

AdminDroid Exchange Online Reporter

Stay Ahead of Mailbox Limits - Monitor Exchange Online Quotas Before They Impact Email Flow!

AdminDroid’s Exchange Online reporting tool helps you monitor mailboxes nearing their quota with ease. By providing deep insights into mailbox size trends, warning thresholds, storage usage, and more, it eliminates the need to rely on complex PowerShell operations.

Monitor Mailbox Size Trends to Prevent Quota Warnings

Use the mailbox size over time report to track mailbox growth and spot those nearing their warning quota to prevent mail flow disruptions in Exchange Online.

Enable Archiving for Exchange Online Mailboxes Nearing Quota

Get the list of non-archived mailboxes, monitor their size growth, and proactively enable archives to prevent them from reaching the warning quota.

Track Shared Mailbox Size to Avoid Licensing Issues

Monitor shared mailbox size, usage percentage, and deleted item count to ensure they stay within the storage limit and avoid the need for additional licensing.

Download All Mailbox Quota Details in a Single Report

Export a comprehensive report of Exchange Online mailboxes quota with details including, mailbox size, license status, warning quota, archive status, and more, for efficient mailbox management.

Instantly Analyze Mailbox Usage from a Unified Dashboard

Get detailed insights on mailboxes over warning quota, storage usage, and monitor other trends from a single Exchange Online mailbox usage dashboard.

Receive Daily Alert Notifications for Mailbox Quota Status

Configure daily mailbox quota notification with details such as mailboxes under the limit, those with warnings issues, and those where send or receive is prohibited, to proactively manage storage and prevent mail flow issues.

Overall, AdminDroid Exchange Online management tool makes it easy to monitor and manage Microsoft 365 mailboxes. It helps track mailbox sizes, activity, and settings, giving admins full control over storage and performance. With clear insights and reports, it helps prevent storage issues and simplifies mailbox management across your Exchange Online environment.

Explore a full range of reporting options

Download Live Demo

Important Tips

For project-based collaboration, use shared mailboxes instead of individual ones to centralize project emails and reduce individual mailbox growth.

Identify licensed shared mailboxes with less than 50 GB of storage, and free up licenses if they are unnecessarily assigned.

Monitor spam traffic and block malicious emails to enhance security and prevent unnecessary storage usage that could lead to quota warnings.

Common Errors and Resolution Steps

Below are common errors and troubleshooting fixes that may occur while tracking or managing mailboxes exceeding the warning quota in Exchange Online.

Error Error occurred: InteractiveBrowserCredential authentication failed: User canceled authentication.

This error occurs while running the script .\GetMailboxUsageAndQuotaReport.ps1 due to failed authentication, typically caused by the user canceling the sign-in process.

Fix when prompted for authentication, grant permission without canceling the sign-in process.

Error Get-Mailbox: The term 'Get-Mailbox' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.

This error occurs when the respective PowerShell module is either not installed, not imported correctly, or the session to Exchange Online is not established.

Fix Run the following commands to install the module, import it, and connect to Exchange Online PowerShell.

Install-Module ExchangeOnlineManagement -Force
Import-Module ExchangeOnlineManagement
Connect-ExchangeOnline

Error The value of property 'IssueWarningQuota' must be less than or equal to that of property 'ProhibitSendQuota.'

This error occurs while customizing the mailbox quota using the Set-Mailbox cmdlet. This issue happens when the IssueWarningQuota is set higher than the ProhibitSendQuota, which violates Exchange Online mailbox quota rules.

Fix Ensure that the IssueWarningQuota value is set lower than the ProhibitSendQuota to comply with Exchange Online quota hierarchy.

Error .\GetMailboxUsageAndQuotaReport.ps1 cannot be loaded because running scripts is disabled on this system.

This error appears because PowerShell's execution policy is set to restrict script execution for security reasons. By default, systems often use the Restricted policy, which prevents any script from running.

Fix To run the script without permanently changing system-wide settings, use the following command. It temporarily sets the execution policy for the session and resets when a new session starts.

Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass

Exchange Online

Frequently Asked Questions

Effectively Monitor and Manage Your Exchange Online Mailbox Quotas

What happens when a mailbox exceeds over the warning quota in Exchange Online?

How to fix mailbox quota exceeded issue in Exchange Online?

How to set an admin alert when a user mailbox hits the warning quotas in EXO?

1. What happens when a mailbox exceeds over the warning quota in Exchange Online?

When a mailbox exceeds the warning quota in Exchange Online, there’s no immediate disruption or data loss. However, if mailbox usage continues to increase and reaches the next quota limits, it can lead to issues such as being unable to send or receive emails. Therefore, understanding the different quota limits and how they work is essential. You can get a clear idea by referring to the details below.

Issue Warning Quota

The Issue Warning Quota is the first threshold in Exchange Online, where the system sends a warning email to the mailbox owner when storage nears its limit.
All email functions still work normally at this stage, but the users are advised to delete or archive old emails to avoid hitting the next limit.
The Issue Warning Quota is 49 GB for Exchange Online Plan 1 and 98 GB for Plan 2.

Prohibit Send Quota

When the mailbox owner fails to delete or archive emails after receiving a warning, continued mailbox growth leads to the next stage, called the Prohibit Send Quota stage.
During this stage, the owner can still receive incoming emails. Any attempt to send an email results in a non-delivery error, notifying the user that their mailbox has exceeded the send limit.
The Prohibit Send Quota is 49.5 GB for Exchange Online Plan 1 and 99 GB for Plan 2.

Prohibit Send and Receive Quota

The mailbox enters the Prohibit Send and Receive stage as the third phase, where the mailbox owner can no longer send or receive emails.
At this stage, incoming emails are being returned to senders with an NDR. The mailbox owner must reduce the mailbox storage consumption to start sending and receiving emails again.
The Prohibit Send and Receive Quota is 50 GB for Exchange Online Plan 1 and 100 GB for Plan 2.

Note: The above phases are applicable to both user mailboxes and shared mailboxes in Exchange Online.

2. How to fix mailbox quota exceeded issue in Exchange Online?

When a user reaches their mailbox quota in Exchange Online, they may no longer be able to send or receive emails, which can significantly disrupt productivity. This can occur if users ignore the warning quota and the mailbox size reaches either the prohibit send or prohibit send and receive quota.

If users receive a warning quota notification, they can reduce the mailbox size by deleting unnecessary emails from the Deleted Items, Junk, etc. However, as an admin, you can also implement the following solutions to help resolve the issue. Before implementing the solutions, first identify the Exchange Online plan assigned to the mailbox, as this helps you understand the mailbox's current features.

Sign in to the Microsoft 365 admin center and go to Users»Active users.
Select the user whose mailbox plan you want to check.
Under Licenses and Apps, check the assigned license (e.g., Microsoft 365 E5).
Click Apps to view enabled services and confirm the Exchange Online Plan listed.

Enable archive mailbox in Exchange Online

Enabling archive for a mailbox helps reduce the size of the primary mailbox. It allows users to move older emails to additional storage for better mailbox management.

Exchange Online Plan 1 offers a 50 GB archive but doesn't support auto-expanding archiving. Plan 2 includes a 100 GB archive that can expand up to 1.5 TB.

Apply retention policy to mailbox

Create and apply retention policies in Exchange Online to automatically clean up or retain mailbox content. This helps control mailbox size and prevents users from reaching the warning quota.

Upgrade Exchange Online mailbox licence

Alternatively, you can upgrade to a higher-tier Exchange Online or Microsoft 365 plan that provides increased mailbox storage capacity. If you are currently on Exchange Online Plan 1, which offers a 50 GB primary mailbox, you can switch to Plan 2, which provides a 100 GB primary mailbox and 1.5 TB of archive mailbox storage. To enable this, you will need to assign a license for Exchange Online Plan 2 to the user, ensuring they benefit from the increased storage.

Increase Exchange Online mailbox quotas (temporary)

Temporarily increasing Exchange Online mailbox quotas can help manage sudden storage needs. It prevents disruptions while a long-term solution such as archiving, cleanup, or license upgrade is implemented.

Exchange Online Plan 1 has default quotas of 49.5 GB (Issue Warning), 49.75 GB (Prohibit Send), and 50 GB (Prohibit Send and Receive), while Plan 2 defaults are 98 GB, 99 GB, and 100 GB, respectively.

Note: The Prohibit Send and Prohibit Send/Receive thresholds must always be set higher than the Issue Warning quota (i.e., Issue Warning < Prohibit Send < Prohibit Send and Receive).

3. How to set an admin alert when a user mailbox hits the warning quotas in EXO?

There is no direct method to send alerts to admins when a mailbox reaches the warning quota in Exchange Online.

As an admin, you need to periodically check mailbox status through the Microsoft 365 admin center or run PowerShell cmdlets to monitor it.

However, AdminDroid simplifies this process by automating quota warning reports and delivering them directly to designated admins.

Ensure timely action without the need for constant manual checks by utilizing AdminDroid's scheduling feature.

To set up a quick schedule, go to the Mailbox Over Warning Quota report under Report»Exchange.
Click the Schedule icon in the top right corner. You can choose the export format and set the frequency to weekly, daily, etc., based on your needs.