Solved: How do I increase Office 365 Mailbox size limits

Exchange Online, which is a part of the Office 365 suite, is an efficient and reliable email service that you can use from any location with web access. But the amount of space in the cloud storage available to store messages is limited. Issues can happen after a user’s Office 365 mailbox runs out of space. A user can miss a critical message, which won’t be delivered due to lack of storage space or even face data loss.

In this guide, we explain Office 365 mailbox size limits and effective solutions to increase the available storage space.

Content Summary

What Happens When a Mailbox Size Limit Is Reached?
Checking Mailbox Size in Outlook Online
Checking Mailbox Size in the Exchange Admin Center
How to Increase the Mailbox Size
Solution 1: Upgrade the Subscription Plan
Solution 2: Edit Quotas
Solution 3: Enable Archiving
How to Enable an Archive Mailbox in the Exchange Admin Center
Solution 4: Delete Unnecessary Data
Solution 5: Use PowerShell
Connect to Exchange Online PowerShell
Create a New Exchange Online Session
Increase Mailbox Size Limit
Commands to Manage Mailbox Sizes in PowerShell: Displaying All Accounts
Commands to Manage Mailbox Sizes in PowerShell: Sorting by Size
Commands to Manage Mailbox Sizes in PowerShell: Changing Quotas for Multiple Users
Commands to Manage Mailbox Sizes in PowerShell: Enabling Mailbox Archiving
Summary

What Happens When a Mailbox Size Limit Is Reached?

There are three limits applied to the mailbox storage quota. Once they are reached, you get notified:

• Warning limit. You receive this notification when Office 365 email storage limits are almost reached. It is a recommendation to delete emails not containing any critical data. In case you don’t free up space, you won’t be able to send new messages.
• Send limit. You can’t send emails. To fix this, delete emails from the mailbox. Note that you can still receive messages when you get this notification.
• Send/receive limit. After this notification, you can’t send or receive emails until you free up space in the email storage. Every sender trying to send an email to your account receives a non-delivery report (NDR).
• As a user, you can check the space available in your own mailbox via Outlook Online.
• As an Office 365 admin, you can check that parameter of any user via the Exchange admin center.

Below we’ll explain both ways.

Checking Mailbox Size in Outlook Online

Step 1: Go to https://outlook.office.com.

Step 2: Sign in to Office 365 using your credentials.

Step3:  Click on the Settings icon located in the top right corner of the Outlook Online interface to open the Settings panel.

Step 4: Click on the View all Outlook settings at the bottom of the display.

Step 5: Go to General > Storage in the Settings window.

Step 6: The space used and the maximum size of the mailbox storage is displayed on the Storage page. Diagram colors categorize emails. Under the diagram, you can see the size of each email folder in Outlook Online.

Checking Mailbox Size in the Exchange Admin Center

Step 1: Go to https://login.microsoftonline.com/jsdisabled to open the Exchange admin center.

Step 2: Sign in to the Exchange admin center using the Office 365 admin account credentials.

Step 3: Check the navigation panel and click on Recipients > Mailboxes.

Step 4: You see a list of Office 365 mailboxes for your organization on the screen. Find and click on the required user account to see the details on the interface panel to the right. In the bottom right corner of the screen, you can see the info about the chosen user’s mailbox size.

How to Increase the Mailbox Size

To increase the size of an Office 365 mailbox, you should meet certain conditions and then choose one of the below solutions. Otherwise, you should archive or delete old emails to get additional free storage space for a mailbox.

Let’s look at the methods.

Solution 1: Upgrade the Subscription Plan

Buying an Office 365 subscription plan of a higher class with extended mailbox limits for Exchange Online. With top subscription plans, your mailbox storage is unlimited. Of course, this means that you have to invest more in Office 365.

Solution 2: Edit Quotas

Administrators can configure quotas for mailboxes and change warning limits, send limits and send/receive limits as required. Nevertheless, the edited quotas can’t exceed the limitations of your current Office 365 subscription plan.

As an Office 365 admin, you can change Office 365 mailbox capacity for every user.

The default notification settings are the following:

• Warning limit: 98% of the maximum mailbox capacity
• Send limit: 99% of the maximum mailbox capacity
• Send/receive limit: 100% of the maximum mailbox capacity

Solution 3: Enable Archiving

With the use of the mailbox archive, you can use additional 50 or 100 GB of cloud space to transfer and store old emails. You don’t need to delete those archived messages.

The most advanced subscription plans of Office 365 provide clients with unlimited storage space for archives. When you’re using this plan, an additional 100 GB of archive space is provided after you use up the previous 100 GB. This feature is called auto-expanding. Keep in mind that you can use that additional mailbox space only to store archived emails. For instance, archiving other users’ emails is not allowed.

The data of the primary mailbox is in the cloud storage but can also be copied to an email client. On the other hand, the archive mailbox data can be stored exclusively in the cloud.

How to Enable an Archive Mailbox in the Exchange Admin Center.

Step 1: In the Exchange admin center’s navigation panel, look for Recipients > Mailboxes and choose the required Office 365 user. After that, you see the panel with the details about the chosen user.

Step 2: Select the Mailbox tab.

Step 3: Click on the Manage mailbox archive option under the More actions section.

Step 4: Toggle on to enable the Mailbox archive option.

Step 5: After you enable the mailbox archive, you can see the bar displaying the utilized storage space in the mailbox archive. The default configuration is set to display a warning message when the archive storage usage hits 90%.

Step 6: Click on the Save button and close the pane.

Solution 4: Delete Unnecessary Data

The data that is no longer needed can be deleted from a mailbox to free up some storage space. In case you don’t have data that you can delete, consider backing up Office 365 emails to a custom location and deleting them from the cloud storage after.

Note: Those who use a client app for emails (for instance, Microsoft Office Outlook) should check whether the emails are deleted from the Outlook Online storage along with the messages in the local client.

If you have POP3 set for email delivery and your mail client is adjusted to store message copies on a server, then the message deleted locally still remains on Microsoft 365 mail servers. To free up space in the cloud storage, you should open the Outlook Online web interface and delete emails from there.

With an account set to use IMAP, your messages in the client and email server get synchronized. That means the messages deleted via the client are deleted from the server storage as well.

In case you configure a client to preserve copies of sent messages on a server via SMTP, look for those messages in Outlook Online. If needed, delete mail messages from the cloud storage to free more Office 365 space.

Solution 5: Use PowerShell

Increasing the size of the Office 365 mailbox with the use of PowerShell is possible for administrators and requires an appropriate subscription plan. You can use the method in case your mailbox still has the old size applied despite Microsoft increasing the maximum limit for your current subscription plan (Microsoft extended the limit in 2013 and 2016 for Office 365 E3 and E5 subscriptions, for instance).

Thus, if your mailbox was created before 2016, you can probably increase your email storage limits in Office 365 from 25 GB to 50 GB and from 50 to 100 GB accordingly. No other limitations are affected when the maximum mailbox size is increased. A number of mailbox folders, sending limitations, address book limits, email size, and other settings remain unchanged.

Read further to find out about PowerShell commands for increasing Office 365 size limits for a mailbox. Additionally, we will show the steps required to enable mailbox archives.

Connect to Exchange Online PowerShell

Step 1: Press the Windows + R key to open the Run dialogue box.

Step 2: Type powershell then press the Ctrl + Shift + Enter key combination to open up an elevated PowerShell window. If the UAC (User Account Control) prompt, click Yes to grant administrator access.

Step 3: Type the following command to connect to Exchange Online PowerShell using Powershell:

$UserCredential = Get-Credential

This connection is needed to enable Exchange Online management with cmdlets. The entered credentials are saved in a variable.

Create a New Exchange Online Session

Step 4: Execute the below command to use the credentials to create an Exchange Online session:

$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection

Import-PSSession $Session -DisableNameChecking

Step 5: Execute the below command to check the mailbox quota for a user:

Get-Mailbox <User ID> | Select *quota

Increase Mailbox Size Limit

Step 6: Execute the following command to increase the mailbox size limit in Office 365:

Set-Mailbox <UserID> -ProhibitSendQuota <Value> -ProhibitSendReceiveQuota <Value> -IssueWarningQuota <Value>

Note: The command takes effect only when the mailbox size extension is supported by your current subscription plan (license).

Where:

• ProhibitSendQuota, ProhibitSendReceiveQuota, and IssueWarningQuota are the corresponding Office 365 mailbox storage quotas.
• The ProhibitSendQuota value must be less or equal to the value of the ProhibitSendReceiveQuota.
• The IssueWarningQuota must be less or equal to the value of the ProhibitSendQuota.
• <UserID> is the email address of the Office 365 user, user principal name, or globally unique identifier (GUID).
• <Value> is the amount of storage in Gigabytes, Megabytes, or Kilobytes (GB, MB, or KB).

In our example, we use the following command:

Set-Mailbox [email protected] -ProhibitSendQuota 98GB -ProhibitSendReceiveQuota 99GB -IssueWarningQuota 97GB

A lower IssueWarningQuota value can be set to timely let the user know that the free space in the mailbox storage is running out.

Commands to Manage Mailbox Sizes in PowerShell: Displaying All Accounts

When you need to check the size of mailboxes in all Office 365 accounts that your organization uses, you can do that via PowerShell. The results are listed in the console output – there is no need to check every user’s properties manually with the use of the admin center GUI.

To use the new module with new commands, establish an Exchange Online connection:

Connect-Exchange-Online

Use this command to download the mailbox data to the variable:

$exomailboxsize = (Get-EXOMailbox | Get-EXOMailboxStatistics)

Commands to Manage Mailbox Sizes in PowerShell: Sorting by Size

Mailboxes can be sorted by size with this cmdlet:

$exomailboxsize | select TotalItemSize, DisplayName | sort -Property TotalItemSize -Descending

The command can be used to identify mailboxes that are running out of storage space (or have run out already).

Commands to Manage Mailbox Sizes in PowerShell: Changing Quotas for Multiple Users

Quotas for the mailboxes of multiple users can be changed with one command. To apply changes to Office 365 mailbox sizes of all users, execute this cmdlet:

Get-Mailbox | Set-Mailbox -ProhibitSendQuota <Value> -ProhibitSendReceiveQuota <Value> -IssueWarningQuota <Value>

Filters can be used to change Office 365 mailbox size limits for the accounts of an entire department:

Get-User | where {$_.Department -eq Department_Name} | Get-Mailbox | Set-Mailbox -ProhibitSendQuota <Value> -ProhibitSendReceiveQuota <Value> -IssueWarningQuota <Value>

After you’ve done your work in Exchange Online, use the following command to close the session in PowerShell:

Remove-PSSession $Session

Commands to Manage Mailbox Sizes in PowerShell: Enabling Mailbox Archiving

You can use PowerShell cmdlets to enable mailbox archiving.

When you need to enable archiving for a particular user, execute the following cmdlet:

Get-mailbox -Identity [email protected] | Enable-Mailbox -Archive

where [email protected] is that user’s domain.

To enable archiving for all mailboxes you manage, use this command:

Get-mailbox -Filter {ArchiveStatus -eq 'none' -and RecipientTypeDetails -eq UserMailbox} | Enable-Mailbox -Archive

To check the configuration mailbox archive in mailboxes, execute this cmdlet:

Get-Mailbox -Archive

When auto-expanding is supported by your current subscription plan, the feature can be enabled with this cmdlet:

Enable-Mailbox -Identity user -AutoExpandingArchive

When users need to free up Office 365 mailbox storage space, they can manually transfer emails to the archive mailbox.

Summary

Exchange Online is a reliable and efficient communication service in Office 365. However, the size of Office 365 mailboxes has limits that depend on your organization’s subscription plan. When the limit of the Office 365 mailbox is reached, a user might not be able to receive or send messages. This guide explained the ways to avoid issues by increasing Office 365 mailbox sizes.