We’re planning a migration from Exchange 2016/2019 to Office 365, and one of the biggest challenges we’re facing is large mailbox sizes. Some of our users have mailboxes well over 100GB, including archives and shared mailboxes.
Using native methods like PowerShell or Microsoft’s built-in migration options has been a struggle:
- Mailbox throttling slows everything down.
- The process often times out or fails with oversized mailboxes.
- Restarting interrupted migrations sometimes leads to duplicate items or re-doing the entire batch.
- Public folders and archives add even more complexity.
Has anyone here successfully handled large-scale Exchange to Office 365 migrations without excessive downtime or data loss?
I’ve been reading about third-party solutions, and some claim to remove size restrictions, allow incremental migration (no duplicates), and support public folder/archive migration in bulk. For example, tools like the Shoviv Exchange to Office 365 Migration Tool seem to be recommended because they let you:
- Add unlimited mailboxes without size limits.
- Resume interrupted migrations without duplication.
- Schedule jobs for off-hours to minimize downtime.
- Handle archives and public folders in one go.
Curious to hear what strategies, tools, or best practices have worked for you when dealing with mailbox size limitations in large migrations?