Migration
How to Avoid Losing Email During a Workspace Migration
Quick Answer
To avoid losing email during migration, keep the old mail system active until new-system data is verified complete, avoid switching MX records prematurely, and keep a short overlap period after cutover as a safety net.
Most email loss during migration happens in the gap between "we switched DNS" and "the data finished moving" - a window that is entirely avoidable with the right sequencing.
Common Causes
- MX records switched before migration was verified complete.
- The old mailbox deleted or deactivated immediately after cutover, with no recovery window.
- Migration tool timeouts on very large mailboxes going unnoticed.
Safe Troubleshooting Steps
- Do not switch MX records until data migration is confirmed complete for every user.
- Spot-check a sample of migrated mailboxes for completeness before cutover.
- Keep the old system active and accessible for a short period after cutover.
- Re-run migration for any mailbox that appears incomplete rather than assuming it finished.
What to Verify
- Migration completeness was checked, not assumed, before MX records changed.
- The old mail system remains available for a short period after cutover.
When Professional Help May Be Useful
For migrations with many users or very large mailboxes, having someone monitor the migration process and verify completeness before DNS cutover meaningfully reduces the risk of lost mail.