Hybrid Migration – What you need to know…..


When using a Hybrid Migration in Office 365 it is known as a ‘true online move’ whereby users remain connected to their mailbox throughout the move. Much like a Virtual Machine being migrated to another host, unnoticeable to the end user.

  • The client switchover is done automatically at the end of the mailbox migration to sustain the above.
  • When using Exchange 2003 this will be a traditional “Offline” move due to the nature of the legacy version.

Outlook uses Autodiscover to detect the ‘move/change’ and resolves this within the Outlook profile automatically on the client machine.

As it is seen as a move (not a new mailbox + data copy), Outlook doesn’t see this as a ‘new/different’ mailbox so the OST will remain intact and as such doesn’t mean an OST has to be re-downloaded, which can cause quite a problem if the OST file happens to be in the tens of gigs.

All moves are paced by the Datacenter, it will define it’s own speed for this migration and you won’t necessarily be moving at the speed of your internet line(s), this is to ensure that you are not throttling either end (although MS has a massive pipe it will be more likely to be throttle your end).

Objects are automatically converted for mail routing after the data has been transferred into the cloud.

  • Mailbox on-prem gets converted to a ‘Mail-enabled user’ automatically.
  • Admin has the power to override this automation and stage the move-then-convert steps.

About Stephen Pothecary
IT Professional and Cloud Evangelist! IT Manager at Comms Group UK Ltd - Managed Services | Solutions | Procurement | Support Services | Cloud | Fujitsu!

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