Let’s preface this post that unlimited archiving in Exchange Online has not been so unlimited since November 2019. The limit for online archiving has been to set a 1 TB for archive mailboxes.
Unfortunately, the said 1 TB limit isn’t visible in UI. No administrative interface exists either to allow tenant administrators to see the state of large archive mailboxes or receive warnings through Office 365 admin portal.
When a user within-place archive gets this message: ‘Your archive mailbox is almost full’ you can remedy it by enabling Auto-Expanding Archive via PowerShell. Here’s the steps:
1. Connect to Exchange Online PowerShell (run as admin)
Import-Module ExchangeOnlineManagement
$UserCredential = Get-Credential
Connect-ExchangeOnline -Credential $UserCredential -ShowProgress $true
2. Run the following command in Exchange Online PowerShell to enable auto-expanding archiving for a specific user.
Enable-Mailbox jdoe@domain.net -AutoExpandingArchive
3. Verify that auto-expanding archiving is enabled
Get-Mailbox jdoe@domain.net | FL AutoExpandingArchiveEnabled
Note: The storage quota for the user’s primary archive mailbox is increased by 10 GB (from 100 GB to 110 GB). The archive warning quota is also increased by 10 GB (from 90 GB to 100 GB).
At the same time the storage quota for the Recoverable Items folder in the user’s primary mailbox is increased by 10 GB (also from 100 GB to 110 GB). The Recoverable Items warning quota is also increased by 10 GB (from 90 GB to 100 GB). These changes are applicable only if the mailbox in on hold or assigned to a retention policy.
