By default, Exchange Online mailboxes have a 100 GB archive mailbox. Once this limit is reached, no additional items can be stored unless auto-expanding archiving is enabled.
Auto-expanding archiving allows the archive mailbox to grow beyond the default size by automatically adding extra storage when needed — useful for long-term storage or users with large volumes of email.
We can enable this feature using PowerShell.
Connect to Exchange Online
Install Exchange Online PowerShell module (if not installed):
Install-Module ExchangeOnlineManagement
Connect-ExchangeOnline
Check the archive settings
Get-Mailbox “[email protected]” | Format-List AutoExpandingArchiveEnabled, ArchiveStatus
Enable auto-expanding archiving
Enable-Mailbox “[email protected]” -AutoExpandingArchive
This enables the archive mailbox to expand beyond 100 GB automatically.
Verify archive settings
Get-Mailbox “[email protected]” | Format-List AutoExpandingArchiveEnabled, ArchiveStatus
Maximum mailbox archive size
| License | Default archive size | Auto-expanding archiving | Max. size with expanding |
|---|---|---|---|
| Exchange Online Plan 1 | 50 GB | ❌ No | – |
| Exchange Online Plan 2 | 100 GB | ✅ Yes | ± 1.5 TB |
| Microsoft 365 E3 (inclusief EOL Plan 2) | 100 GB | ✅ Yes | ± 1.5 TB |
| Microsoft 365 E5 (inclusief EOL Plan 2) | 100 GB | ✅ Yes | ± 1.5 TB |
| Microsoft 365 Business Standard / Premium | 50 GB | ❌ No | – |
| Exchange Online Archiving Add-on | 100 GB | ✅ Yes (for P1 mailbox) | ± 1.5 TB |
| Office 365 E3 met Archiving Add-on | 100 GB | ✅ Yes | ± 1.5 TB |