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Microsoft has designed its Office 365 subscription plans to accommodate the needs of each business regardless of its employee strength or software requirements. There are various plans for Office 365 where the size of the mailbox is different. The Enterprise plans have more space than the Business plans. You should check the following table showing the maximum storage limit for various mailboxes in each plan.

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.

Change your Office 365 subscription plan

The most straightforward approach to double the storage space of user mailboxes is to change the subscription plan from Business to Enterprise. If you check the storage limits table, you can see that Business Basic and Business Standard have 50 GB of storage. If you upgrade the plan to Enterprise E1, E3, and E5, the storage limit will automatically increase 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

After you have upgraded your subscription plan, if the user mailbox limit is set to 50, you must increase it manually. Some organizations allow the administrator to change the mailbox size manually. Use the following steps-

  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 Export Office 365 to PST.



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 take a free Office 365 backup mailbox data first.