M365 Exchange Online | Archive: 3 TB instead of 1.5 TB

The auto-expanding archive in Exchange Online is increasing from 1.5 TB to 3 TB for eligible mailboxes. According to the Message Center, the global rollout (MC1472592) has been underway since mid-October 2026 and is expected to be completed by the end of October.

MC1521615 dated October 22 adds the schedule for Government Clouds: GCC, GCC High, and DoD will follow from mid-November, with completion planned for early December 2026.

The limit is tied to the license, not the mailbox. Eligible are Office 365 and Microsoft 365 E5, A5, and G5, the Microsoft 365 Purview Suite, Defender + Purview Suite FLW, Microsoft 365 F5 Compliance, F5 Security + Compliance, as well as the combination of the mini-suites eDiscovery & Audit, Insider Risk Management, and Information Protection & Governance.

Mailboxes with E3, A3, or G3 remain at 1.5 TB. As an admin, you cannot change the quota, and Microsoft does not specify any additional costs.

The limits of technology do not change. According to Microsoft Learn, an archive can grow by a maximum of 1 GB per day. An archive is only expanded once the archive or Recoverable Items reach 90 GB, and provisioning can take up to 30 days.

The feature can only be enabled via Exchange Online PowerShell and cannot be reversed. After that, inactive mailboxes can no longer be restored. You can only export their data via content search.

For hybrid mailboxes with an on-premises primary mailbox and a cloud archive, Enable-Mailbox -AutoExpandingArchive does not work. In this case, you need to use Set-OrganizationConfig -AutoExpandingArchive. After enabling this organization-wide switch, AutoExpandingArchiveEnabled on the individual mailbox will remain False—this is expected behavior.

Whether the statistics for auto-expanding archives show the sum of all containers is not specified in the cmdlet documentation. Compare the number with a test mailbox before building reports based on it.

The effect depends on the license. Look for mailboxes with large archives that don’t have an eligible license, as those will remain capped at 1.5 TB, and your retention strategy must account for that.

Those using the archive as long-term storage should plan governance now, not just before hitting the limit. Growth is capped at 1 GB per day anyway, so an archive won’t fill up overnight—but importing large legacy data will take time accordingly.