Online archive

Hi @Ian Roy 

According to Learn about auto-expanding archiving | Microsoft Learn, auto‑expanding archiving in Exchange Online automatically increases archive mailbox storage when the archive reaches its capacity, supporting long‑term retention requirements.

Prerequisites 

Before enabling auto-expanding archiving, verify the following: 

1.Each user must have a license that includes Exchange Online Archiving. Supported options: 

-Exchange Online Plan 2 

-Microsoft 365 E3 or E5 

-Exchange Online Archiving add-on (for Exchange Online Plan 1) 

2.The user must already have an Online Archive. If not, create one first. 

3.You must have one of the following roles: 

-Global Administrator 

-Exchange Administrator 

-Recipient Management 

4.You need to connect via Exchange Online PowerShell. 

Note: Once enabled, auto-expanding archiving cannot be disabled.  

Here are steps to enable auto-expanding archiving using Exchange Online PowerShell: 

Install-Module ExchangeOnlineManagement 
Connect-ExchangeOnline 
# Enable an Archive Mailbox if not already enabled 
Enable-Mailbox -Identity ******@domain.com -Archive  
# Enable auto-expanding archiving for a specific user 
Enable-Mailbox -Identity ******@domain.com -AutoExpandingArchive  
# Verify settings 
Get-Mailbox ******@domain.com |   
Format-List DisplayName,ArchiveStatus,AutoExpandingArchiveEnabled  

# Enable organization‑wide:
Set-OrganizationConfig -AutoExpandingArchive
# Verify configuration 
Get-OrganizationConfig | Format-List AutoExpandingArchiveEnabled

# Enable auto-expanding archiving for all mailboxes with active archives 
Get-Mailbox -ResultSize Unlimited -Filter {ArchiveStatus -eq "Active"} |  
ForEach-Object {  
    Enable-Mailbox -Identity $_.UserPrincipalName -AutoExpandingArchive  
} 

Reference: Enable auto-expanding archiving | Microsoft Learn 

I hope this information is helpful. 

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