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Learn How to Increase Office 365 Mailbox Size Limits Using the Right Way

Published By Nilesh Kumar
Debasish Pramanik
Approved By Debasish Pramanik
Published On April 24th, 2024
Reading Time 8 Minutes Reading
Category Office 365

This guide is specially dedicated to recent user queries i.e. “How to increase Office 365 mailbox size limit?” In this write-up, we are going to explain the top 3 ways using which, you can easily perform this task without any hassle.

Outlook is one of the most popular applications of the Microsoft 365 suite and is extensively used by both individuals and organizations for sharing emails, scheduling meetings, organizing calendars, and much more.

Outlook has become such an integral part of the organizational setup that even a small disruption in its services has the potential to cause a major loss of business, clients, and reputation.

Now, you may wonder if you have purchased a well-rounded O365 subscription plan as per your organizational needs. It was working fine till now but suddenly started showing warning alerts and error messages. Don’t panic, your subscription is right in place, it could be just that your mailbox has exceeded its allowed limits. Let us explain.

Every Microsoft subscription plan comes with different mailbox size limits, which may further vary with the type of user’s license and mailbox type. The average mailbox capacity for most O365 subscription options is around 50 gigabytes (GB). When you reach the maximum capacity of your Office 365 subscription plans, you may not be able to send or receive messages.

This may cause you to lose out on some important emails and data. The mailbox can again be made functional by deleting unnecessary emails from it or archiving old emails. However, both these are only temporary solutions, which also demand a lot of time and effort. The best solution is to increase the size of your mailbox to make it capable of holding more data. Now there are again multiple ways to achieve the same.

We will cover all methods in this article, but before that let us know how to check the size of our mailbox.

How to Check the Size of the Office 365 Mailbox?

Most businesses run for 24 hours and even a small delay can cause major losses. So, to take timely action and avoid any disruption in O365 mailing services, you need to know your actual mailbox size and how much space is left in there.

Fortunately, Microsoft allows us to check this in a few simple steps:

(Applicable on Outlook for Microsoft 365, Outlook 2021, Outlook 2019, Outlook 2016, & Outlook 2013)

  • Step 1. Go to the Mail view, and click your account.
  • Step 2. Click the Folder tab and then select Folder Properties.
  • Step 3. In the General tab of the Properties pane, click the Folder Size button.
  • Step 4. The size of your mailbox and each subfolder appears (in KB).
  • Step 5. To get the size in MB, you need to divide the KB value by 1024.

3 Different Ways to Increase Office 365 Mailbox Size

  • Using a Professional Backup Solution
  • Upgrading the Office 365 Subscription Plan
  • Using PowerShell Commands

As we have already mentioned, it is not always possible to keep deleting emails to free up storage space or archive old data, and there must be some other ways to increase the size of the mailbox. So here they are:

Method 1- Use Expert-recommended Professional Solution

This will provide an unlimited amount of storage space without you ever having to upgrade your subscription plan. Office 365 Backup Tool allows you to export all your O365 mailbox data in PST format and store it at a safe location on your computer or even on an external storage device.

This will empty your mailbox. As the tool comes with a lifetime license and free upgrades, you can backup and migrate your O365 mailbox data as many times as you want, and never again face any mailbox size issues.

Download Now Purchase Now

Download the Free Demo version of the tool to check its various unique features and functionalities.

Benefits of Increasing Office 365 Mailbox Size Limits

Apart from facilitating the normal functioning of email services, having an adequate amount of space in mailboxes allows users to:

  • It becomes comparatively easy to arrange your mailbox data in a more organized way.
  • You can effortlessly locate important information easily when required.
  • You can be worry-free about the possibility of accidentally deleting any crucial mail.
  • It allows you to better collaborate by being able to share large files, attachments, etc.
  • Most importantly, you can focus on your work as you no longer need to spend time managing your mailboxes.

Software Steps to Increase Office 365 Mailbox Size To 100GB

  • Step 1. Download the tool and launch it on your Windows computer. Choose Office 365 as the source and Outlook as the destination.
    provide source and destination
  • Step 2. Enable the required workload from the given options such as emails, contacts, calendars, and documents. Apply the date filter, if required.
    select category and apply date range filters
  • Step 3. Use the source Office 365 admin account credentials such as Admin Email and Application ID. Validate the required permissions and once done then click on Next.
    provide office 365 details and validate
  • Step 4. Select the destination account to save the backup file and choose the file size accordingly. Validate the required permissions and once done then click on Next.
    provide destination path and validate the necessary permissions
  • Step 5. Add users and validate the required license permissions.
    add users
  • Step 6- Lastly tap on the “start backup” and then “start” to increase Office 365 mailbox size.

Method 2- Upgrade your O365 Subscription Plan

Unless there is a real or long-standing requirement for a lot of storage space to meet the needs of your expanding business, this way is not very appealing to most users. It is not a one-time or cost-effective solution as you may need to upgrade your plan repeatedly to accommodate your growing requirements.

Method 3- Use PowerShell Commands

However, there are limitations to this method. The Office 365 mailbox size 365 can be increased in PowerShell only if the subscription plan taken by the user supports this operation. It is important to note that PowerShell does not increase the size of your mailbox. It allows the storage space that is already there in your subscription plan. For example, you have been allotted 50 GB of storage space in your subscription plan, but until now, you have used only 10 GB of it.

Now, when you need more storage space to accommodate your growing requirements, Microsoft 365 admin allows you the remaining 40 GB (in batches), and this can be done with the help of PowerShell commands. So this means that once your allotted limit ends, even PowerShell cannot increase it further. Moreover, working with PowerShell commands is a complex procedure and needs technical expertise on the part of the user to handle it efficiently as any error can cause permanent loss of your crucial data.

Using PowerShell Commands to Increase Microsoft 365 Mailbox Size

Follow these steps to increase the size of your Office 365 Mailbox:

Step 1. Select the icon of the Windows PowerShell application. Right-click and select the Run as administrator option.

Step 2. Now, run the following command:

$UserCredential = Get-Credential

Step 3. Enter the credentials of your Office 365 account in the credentials request dialog box.

Step 4. Now, create a new Exchange Online session and run the following command;

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

Step 5. Run the following command to import the Exchange Online cmdlets for the local session:

Import-PSSession $Session -DisableNameChecking

Step 6. To get the size limits of your current mailbox, run this command.

Get-Mailbox < User ID > | Select *quota

Step 7. Now to increase Office 365 mailbox size from 50 GB to 100 GB, you need to run the following command:

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

Let us take an example:

Set-Mailbox charlie@yourmail.com -ProhibitSendQuota 99GB -ProhibitSendReceiveQuota 98GB -IssueWarningQuota 98GB

In this command, you are setting the Warning Limit quota at 98 GB and the Send quota at 99 GB. This means you will now have 100 GB of storage in your mailbox.

In case, you wish to apply these changes to multiple users, you need to run the following command:

Get-User | where {$_.Team -eq “Developer”} | Get-Mailbox | Set-Mailbox -ProhibitSendQuota 99GB -ProhibitSendReceiveQuota 98GB -IssueWarningQuota 98 GB

In the above command, we have increased the O365 mailbox size of the entire team up to 100 GB.

Step 8. Once you are done with all the changes, run the following command to end the session:

Remove-PSSession $Session

Also, Read – How to Backup Shared Mailbox in Office 365.


In this article, we have dealt with one of the most common concerns of nearly all Office 365 subscribers, i.e., how to increase the size of an Office 365 mailbox. We have explained both manual as well as professional solutions to allow users to increase the capacity of their O365 mailboxes.

Apart from purchasing an upgraded subscription plan, using PowerShell commands is the only option by which we can extend the limits of our O365 mailboxes. As the process is highly complex and technical, ensure that you configure these settings very carefully as even a small error can cause irretrievable data loss.

To avoid any such mishap, it is advised that you should always go for the expert-certified professional solution to increase Office 365 mailbox size and enjoy unlimited storage space.


By Nilesh Kumar

As a Chief Technical Writer, I know the technical issues faced by home and professional users. So, I decided to share all my knowledge via this blog. I love to help you with challenges while dealing with technical jargon.