Exchange Connection Problems

Fix Exchange Online PowerShell Arithmetic Overflow for Mailboxes

Tauseeq Magsi Oct 10, 2026 869 views

Question details

Users experience an arithmetic overflow error when attempting to retrieve mailbox folder statistics using Exchange PowerShell commands.

How to Fix Exchange Online PowerShell Arithmetic Overflow for a Mailbox

Product: Exchange Online PowerShell
Device & OS: not provided
Scenario: Running Get-MailboxFolderStatistics or Get-EXOMailboxFolderStatistics on a specific user's mailbox that contains substantial data in Deleted Items.
Observed behavior: The command fails and returns an arithmetic overflow error, regardless of the client machine, operating system, or PowerShell version being used.

Before you start

Ensure you are connected to the Exchange Online PowerShell module with the necessary administrator credentials before running diagnostic cmdlets.

Solution 1Recommended

Check Recoverable Items and Audits Folder Size

Identify if the arithmetic overflow is caused by an excessively large number of items in the Recoverable Items or Audits folder due to retention holds.

Arithmetic overflow errors in mailbox folder statistics typically occur when a specific subfolder, such as the Audits folder within Recoverable Items, accumulates an unusually large number of items. This is often the result of active retention policies or litigation holds preserving records indefinitely.

Connect to Exchange Online

Open PowerShell as an administrator and connect to your Exchange Online tenant using your admin credentials.

Run Folder Statistics Cmdlet

Execute the following command to check the Audits folder size specifically: Get-MailboxFolderStatistics -Identity <MailboxIdentity> -FolderScope RecoverableItems | Where-Object {$_.Name -eq 'Audits'} | Format-List FolderPath,FolderSize,ItemsInFolder

Analyze the Output

Review the returned FolderSize and ItemsInFolder values. If they are exceptionally high, this is likely the root cause of the arithmetic overflow.

Review Retention Policies

Check the Microsoft 365 Compliance Center for any litigation holds or retention policies applied to the mailbox that might be preventing audit records from being purged.

Check Recoverable Items and Audits Folder Size

Retention Policy Impact: If a hold or retention policy is active, audit records may be retained much longer than normal, causing the folder to grow excessively large over time.

Solution 2

Contact Microsoft Exchange Support

Escalate the issue to Microsoft Support if the error persists or if you cannot clear the overflowed folder manually.

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Frequently Asked Questions

What causes the arithmetic overflow error in Get-MailboxFolderStatistics?

This error generally occurs when a specific folder, frequently the Audits subfolder within Recoverable Items, accumulates a massive amount of data or items that exceeds the numerical limit the PowerShell cmdlet is designed to calculate.

How do litigation holds affect mailbox folder sizes?

Litigation holds and retention policies are designed to prevent items from being permanently deleted. Consequently, data in the Recoverable Items and Audits folders can grow exponentially over time, which may eventually lead to overflow errors when calculating folder statistics.

Are there alternative commands to check mailbox size without triggering the overflow?

Yes, you can use the Get-EXOMailboxStatistics cmdlet instead. This command provides a high-level overview of the total mailbox size and item count without iterating through individual problem folders, thereby bypassing the arithmetic overflow trigger.

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