How do I minimize downtime when migrating public folders to Office 365?

Question

At what point should you migrate public folders from Exchange 2007/2010 to Office 365 to minimize downtime during a cutover migration? I understand from the guide here that you should migrate mailboxes first but it's not exactly clear.

When I migrate mailboxes over, finalize the migration batch and change the necessary autodiscover records, will Outlook reconfigure itself and continue to display the legacy on-premises public folders?

Just worried that once I have migrated mailboxes, Outlook will stop display the public folders altogether. Would prefer not to end up on the spot in a rush to migrate the public folders when they suddenly vanish unexpectedly.

Obviously not Googling the right questions here, so any help would be appreciated.

Answer 1

First - use the legacy method to create a proxy for your Public folders. This will allow your migrated users to access on-prem Public folders thru Outlook Desktop client. ( https://technet.microsoft.com/en-us/library/dn249373%28v=exchg.150%29.aspx )

Migrate all your users to O365. Then you can go back and migrate the public folders.

At this point the only down time for PF's should be when you complete the move request.

The reason for doing this last is because if you migrate them early - any users till on-prem can't access the Public Folders at all. By using the proxy method and migrating them last - you can maintain access to these folders thru your migration period.