How to Increase Office 365 Mailbox Size?

Megha Sharma    Megha Sharma     Updated On - 30 May 2019

Microsoft has set a default size for mailboxes in different Office 365 plans. These are important considerations which an Office 365 administrators should consider for the proper functioning of the Office 365 mailboxes. Here is the default mailbox size for different Office 365 plans.

Office 365 Plan

Default Size of Mailboxes

  • Office 365 Business Essentials
  • Office 365 Business Premium
  • Office 365 Enterprise E1
  • Office 365 Enterprise E3
  • Office 365 Enterprise E5
  • Office 365 Enterprise F1
  • 50 GB
  • 50 GB
  • 50 GB
  • 100 GB
  • 100 GB
  • 2 GB

Note: Microsoft has set a default size for archive mailboxes, shared mailboxes, resource mailboxes, site mailboxes, public folder mailboxes, and group mailboxes also

This default size can be increased or decreased as per the user requirements. More often, users seek to increase the size depending upon the conditions and needs. Some of the primary situations are:

  • Mailbox sizes are already hitting the set or default size limit
  • To make space available for a long-time healthy use of mailboxes without interruptions

We can carry out the steps described below to increase the size of the Office 365 mailboxes from the current set sizes.

Increase Office 365 Mailbox Size through Windows PowerShell

Running Set-Mailbox cmdlets in Exchange Online PowerShell is the way to increase the Office 365 mailbox size. For this, users must run Windows PowerShell as administrator and, connect to Exchange Online with the following command.

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


A dialogue box will get open, Here, enter the Office 365 account administrator credentials and click OK.

Run this command to import the Remote PowerShell session.

Import-PSSession $Session -DisableNameChecking


To set the size for a particular mailbox, run this command.

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


Note: You can check the values of mailbox quota by running: Get-Mailbox < User ID > | Select *quota

If you want to set the maximum mailbox size for all the mailboxes in the account altogether, execute this command.

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


Users can increase their Office 365 mailbox size anytime using these methods. To know more about the mailbox storage limits, visit https://docs.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits#mailbox-storage-limits