ISSUE: Mailbox move failed with QuotaExceededException

Overview

The error below occurs during the Move Mailbox migration step.

"Status is Failed and Status Detail is FailedMAPI. Failure message is QuotaExceededException"

Cause

Microsoft has few limitations which can cause mentioned error:

1. Assigned license giving less mailbox volume that actual mailbox size

2. Shared mailbox has more data that allowed 50GB in O365

3. Mailbox onprem contains folder that has over 1 000 000 items in it. Microsoft will not allow more than 999 999 emails in one folder.

Solution

1. Make sure that correct license with sufficient volume is assign to user account

2. Make sure Shared mailbox is converted into UserMailbox if the mailbox size is over 50GB onprem.

3. Check the folder for mailbox and either:

             a. delete some emails

             b. move the emails from one folder into multiple

You can check the folder size via powershell scripts in this article: Get-MailboxFolderStatistics (ExchangePowerShell) | Microsoft Docs