When you move email between Google Workspace and Microsoft 365, you rarely need to bring every message across. A common plan is to migrate a recent window (one to three years), export the full history to an archive you control, check it opens, and only then cancel the old system. The deadline is set by the old vendor: Google deletes data after cancellation and says it can’t be restored; most Microsoft 365 business subscriptions give 30 days of normal access and then 90 admin-only days before deletion.
Three choices for each mailbox
| Choice | When it fits | Watch for |
|---|---|---|
| Migrate into the new system | Recent mail people still use; active shared mailboxes | Storage limits and migration time grow with history |
| Archive as an export you control | Older mail you must keep or might need | Make sure it is searchable and someone owns it |
| Let it go | Mail past every retention rule and with no other value | Check legal holds and contracts first |
Ex-employee mailboxes are the usual problem: they are often kept on paid licences for years. Export them instead.
Old-vendor deletion timelines
Leaving Google Workspace. Google warns that after you cancel, users’ data will be deleted and can’t be restored, and tells admins to download data first. Its Data Export tool requires an active subscription for core data such as Gmail and Drive, an admin account at least 30 days old with 2-Step Verification, and takes typically 72 hours and up to 14 days. Exports are deleted automatically 60 days after they start, so copy them to your own storage.
Leaving Microsoft 365. Most business subscriptions move from Active to Expired (30 days, users keep access) to Disabled (90 days, only admins can access and back up data) to Deleted. Some enterprise agreements have a 90-day Expired stage. If you delete the subscription outright, SharePoint and OneDrive data is deleted immediately.
What you must keep
Your retention policy should drive what is archived. The IRS asks businesses to keep most tax records for three years and employment tax records for at least four. Contracts, regulators and litigation holds can require more. Email that supports those records belongs in the archive.
The archive after the move
Most companies end up paying to store an email archive nobody opens. Before you do, consider what it is: years of real work between your staff, customers and vendors. Some AI developers license de-identified copies of company email and related records from established US companies, and Mercor, for example, lists Gmail and Outlook among the tools it connects to. Decide this while the old system still exists, and with your lawyer if the mail includes client or patient information.
Questions people ask
Should we migrate all old email into the new system?
Usually not. Migrating years of mail slows the project and costs storage in the new system. Most teams move a recent window, such as one to three years, and archive the rest in a searchable export.
How long do we have after cancelling the old system?
For Google Workspace, assume none: Google says data is deleted after cancellation and can't be restored. For most Microsoft 365 business subscriptions, there are about 120 days of grace, but finish exports before you cancel.
Sources
Related guides
Slack to Teams: what happens to your message history
What Slack lets you export on each plan, what Microsoft Teams can and cannot import, and how to keep years of Slack history when you switch.
What to do with company email, Slack and files when you close
How Google Workspace, Microsoft 365 and Slack delete data after you cancel, how to export first, what to keep, and what the archive may be worth.
Offboarding employee accounts after a layoff without losing data
Suspend, archive, transfer or delete: what happens to a departing employee's Google Workspace or Microsoft 365 account, and the restore windows to know.
Part of Migrating systems.