Migrating large mail items to Office 365

 Important: The steps in this article require that you connect to Office 365 with Windows PowerShell. Refer to the Connect to Office 365 PowerShell article from Microsoft for detailed steps on how to connect to Office 365 using Windows PowerShell.

To migrate items to Office 365 that are larger than th​e EWS defaults, you will need to run the following PowerShell scripts.

First, you should run this script against your Office 365 environment to determine what your current settings are:

Get-Mailbox testuser01 | fl mailboxplan,maxsendsize,maxreceivesize


  • The user can be any standard user on Office 365 that has an Office 365 license assigned that contains a mailbox license.
  • It should be a user whose settings have not been previously modified.

Example results:

MailboxPlan: ExchangeOnlineEnterprise-4b910ff9-8b91-4f2e-960c-302a90c95668
MaxSendSize: 35 MB (36,700,160 bytes)
MaxReceiveSize: 36 MB (37,748,736 bytes)

Next, run this script against your Office 365 environment to set the Mailbox Plan, the Max Send Size and the Max Receive Size:

Get-MailboxPlan | Set-MailboxPlan -MaxSendSize 150MB -MaxReceiveSize 150MB

Note: New users created after you change the mailbox plan will have 150MB as the max send and receive size. However, the current user will still have 35MB. To increase the limit for all users you can run:

Get-Mailbox | Set-Mailbox -MaxReceiveSize 150MB -MaxSendSize 150MB

The example below shows how you can validate that the new limits are applied:

PS C:\Windows\system32> Get-Mailbox testuser01 | fl mailboxplan,maxsendsize,maxreceivesize
MailboxPlan: ExchangeOnlineEnterprise-4e910ff9-8b91-4f2e-960c-302a90c65668
MaxSendSize: 150 MB (157,286,400 bytes)
MaxReceiveSize: 150 MB (157,286,400 bytes)


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