How to Increase Office 365 Mailbox Size to 100 GB

Himanshu Goyal
Himanshu Goyal | Updated On - 19 Mar 2021 |

Read time 4 min

The Microsoft 365 subscription plans vary in their price and given benefits. The default size of the single mailbox is also different in the variety of plans. Business and Enterprise users get more space, and personal users get a little bit lower.

Thus, when the mailbox size of your mailboxes exceeds 50 GB, the organization has only two options left – either upgrade the Office 365 subscription or delete data from the mailbox. But, deleting data is not always an option for many. Also, not every user wants to invest in upgrading the plan due to higher costs.

So, what are options to increase Office 365 mailbox size to 100 GB without upgrading the license? Well, here we have an ultimate solution that allows you to increase Office 365 mailbox size from 50 GB to 100 GB.

Increase Office 365 Mailbox Size using PowerShell

One way to increase the mailbox size limit is by using Exchange PowerShell cmdlets. But, for that, you need to run PowerShell as administrator and connect to Exchange Online (Office 365) with Windows PowerShell.

Increasing Single User Mailbox Size Limit
  1. First, connect to Exchange Online and run PowerShell. Use the below command to increase single user mailbox size.
    Set-Mailbox <UserID> -ProhibitSendQuota <Value> -ProhibitSendReceiveQuota <Value> -IssueWarningQuota <Value>

    Here the parameters <UserID> represents user’s mailbox or email address, <Value> represents the sizes in GB, MB, or KB.
    So, to set the mailbox size limit to 100 GB, you can set the send limit at 99 GB.

  2. Now, use the following command to check the size of the mailbox.
    Get-Mailbox <UserID> | Select *quota

That’s how you can extend the limit for single user mailbox in Exchange Online. If you want to increase the mailbox size for multiple users, then follow the below steps.

Increasing Mailbox Size Limit for Multiple Users
  1. To increase the size of multiple user mailboxes, connect to Exchange Online and use the below command in Windows PowerShell.
    Get-Mailbox | Set-Mailbox -ProhibitSendQuota <Value> -ProhibitSendReceiveQuota <Value> -IssueWarningQuota <Value>
  2. You can also apply additional filters to the Get-Mailbox cmdlet. Below is an example that shows how you can filter on the cmdlets.
    Get-User | where {$_. Department -eq “Sales”} | Get-Mailbox | Set-Mailbox -ProhibitSendQuota <Value> -ProhibitSendReceiveQuota <Value> -IssueWarningQuota <Value>

In this example, three cmdlets are used to filter the commands of an organization’s sales department. The “Where” parameters define the department where the changes will be implemented, “ProhibitSendQuota” parameter defines the set quota limit for a user mailbox, and the “IssueWarningQuota” defines when a user will receive the exceed mailbox size limit warning.

And, here also you can set the send limit at 99 GB.

When the mailbox size limit exceeds for Office 365 users, they start receiving “mailbox size limit exceeded” warning. In such circumstances, using the above PowerShell commands can be very helpful to quickly expand the size limit of your Office 365 mailboxes.

However, if you’re unable to increase the mailbox size, then you’ll have to delete the existing data. This can be done after backing up the existing data safely. And if you want to backup mailbox data, then there is a brilliant solution for that – Kernel Office 365 Backup & Restore.


Expanding user mailbox size limit in Office 365 becomes crucial when it is close to exceeding the present limit. This can be done using PowerShell cmdlets. However, if you think of deleting some items from the Office 365 mailbox to keep the mailbox growth in check, it is a good practice to back up the mailbox data first. And for this, you can use Office 365 Backup & Restore tool.