In Microsoft 365 (M365), auto-expanding archiving allows an archive mailbox to grow beyond the default 100 GB limit. When a user’s archive mailbox reaches this threshold, the system automatically enables additional storage in increments (typically 50 GB at a time), up to 1.5 TB or more.
You must manually enable it per mailbox using PowerShell.
🔧 Steps to Enable Auto-Expanding Archive
1. Connect to Exchange Online PowerShell
Open PowerShell and run:
Connect-ExchangeOnline -UserPrincipalName admin@yourdomain.com
2. Enable Archive Mailbox (if not already enabled)
Enable-Mailbox -Identity user@domain.com -Archive
3. Enable Auto-Expanding Archive
Enable-Mailbox -Identity user@domain.com -AutoExpandingArchive
Replace
user@domain.comwith the actual mailbox identity.
🔍 To Check If Auto-Expanding is Enabled
Get-Mailbox -Identity user@domain.com | Select-Object ArchiveStatus, AutoExpandingArchiveEnabled
⚠️ Important Notes:
- Auto-expanding archiving is only supported in Microsoft 365 E3/E5 or equivalent Exchange Online plans.
- It may take up to 30 days for additional storage to be provisioned once the archive is full.
- PST files can be imported to archive mailboxes to offload primary mailbox storage.