Exchange Online: move items from Online Archive back to primary mailbox (same folders) without leaving duplicates in the archive

Hi everyone,

We have a requirement to move all items from a user’s Online Archive back to their primary mailbox in Exchange Online, keeping the same folder structure, and without leaving copies in the archive. The archive must stay enabled.

Environment

• Exchange Online (Microsoft 365), cloud mailbox
• Primary quota: 100 GB, current usage about 12 GB
• Archive: about 21 GB, about 41,000 items (not auto-expanding)
• The retention policy has been changed so that items won’t be re-archived. A retention hold was used during the process.

What we tested (in a test tenant)

powershell

New-MailboxRestoreRequest -SourceMailbox <ExchangeGuid> -SourceIsArchive `
  -TargetMailbox <ExchangeGuid> -ExcludeDumpster -AllowLegacyDNMismatch `
  -ExcludeFolders "#DeletedItems#/*","#JunkEmail#/*"

• Completed with DataConsistencyScore: Perfect, and all items transferred.
• Mail items were restored into the matching folders in the primary mailbox, as expected.

Issues

1. New-MailboxRestoreRequest copies the items. The originals remain in the archive, so the data is duplicated and uses space in both the primary and the archive.
2. Calendar items from the archive were restored into a new “Calendar_0” folder instead of merging into the existing Calendar.

What we’ve ruled out for removing the archive copies

• Search-Mailbox -DeleteContent: retired in Exchange Online.
• New-ComplianceSearchAction -Purge: limited to 10 items per mailbox per action, which is impractical for about 41,000 items.
• EWS-based scripts: EWS is being retired in Exchange Online.
• Disabling the archive: not acceptable, since the archive must stay enabled.

Questions

1. Is there a supported server-side way to move (not copy) items from the Online Archive to the primary mailbox, keeping the folder structure?
2. If not, what is the recommended supported method to bulk-remove the archive copies after a successful restore request, apart from deleting or emptying folders manually in Outlook or OWA?
3. Is there a way to make calendar items merge into the existing Calendar folder instead of creating “Calendar_0”?

Any guidance or official documentation would be appreciated.Exchange Online: move items from Online Archive back to primary mailbox (same folders) without leaving duplicates in the archive