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How to Set Default Exchange Online Mailbox Size Limits for New Users

Maira Mehtab Sep 22, 2026 870 views

Question details

The administrator needs to automatically enforce a 50 MB maximum send and receive limit on all newly created Exchange Online mailboxes without having to apply manual changes or use recurring scripts.

Product: Exchange Online
Device & OS: not provided
Scenario: Configuring tenant-wide default mailbox plans for new user account creation.
Observed behavior: Newly created mailboxes do not have the desired 50 MB size restrictions by default, requiring continuous administrative intervention to enforce.

Before you start

Ensure you have the necessary administrative privileges in your Microsoft 365 tenant and that you have installed the Exchange Online PowerShell V2 (EXO V2) module to execute the required commands.

Solution 1Recommended

Configure Mailbox Plan via Exchange Online PowerShell

Use Exchange Online PowerShell to update the default mailbox plan, which will automatically apply the specified size limits to all future mailboxes created in the tenant.

Exchange Online utilizes Mailbox Plans as templates when creating new user mailboxes. By altering the default mailbox plan, administrators can ensure that standard limits are applied from the moment a mailbox is provisioned.

Connect to Exchange Online PowerShell

Open PowerShell as an administrator and run the command `Connect-ExchangeOnline` to log in with your global administrator or Exchange administrator credentials.

Update the default mailbox plan limits

Execute the command `Set-MailboxPlan -MaxSendSize 50MB -MaxReceiveSize 50MB` to modify the default template limits.

Verify the configuration

Create a new test user in your Microsoft 365 admin center, then use Exchange Online PowerShell to confirm the test user has been assigned the updated mailbox plan and accurately reflects the 50 MB limits.

Impact on existing users: Modifying the mailbox plan only affects newly created mailboxes. It does not retroactively change the send and receive limits for existing users in your organization.

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Frequently Asked Questions

Does updating the mailbox plan affect existing Exchange Online users?

No, running the `Set-MailboxPlan` command only applies the specified settings to mailboxes created after the command is executed. To change limits for existing users, you must use the `Set-Mailbox` command.

How can I verify the current default limits on my mailbox plans?

You can view the current limits applied to your mailbox plans by executing the `Get-MailboxPlan | Format-List Name, MaxSendSize, MaxReceiveSize` command in Exchange Online PowerShell.

What should I do if the limits are not applying to new users?

If the limits fail to apply, confirm that the new users are actually being assigned the mailbox plan you modified. You can check a specific user's assigned plan by running `Get-Mailbox -Identity <user> | Select-Object MailboxPlan`.

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