In this week’s special guest episode of the Practical 365 Podcast, Sigi Jagott is joined by fellow writer and Office 365 migrations expert, Mike Weaver. The two deliberate over migrating Exchange Mailbox Permissions in an Office 365 tenant to tenant migration. This is an area of Microsoft 365 which has seen a substantial uptick recently due to the proliferation of business merger, acquisition and divestiture activity.

In Mike’s line of work, as Director of Enterprise Migrations for Quadrotech, he says the ‘MAD’ (Mergers, Acquisitions & Divestitures) activity, has exploded in recent years. And during this time, the usage of Microsoft 365 has been rapid across the globe.

Consequently, IT admins are now faced with a new challenge, a combination of the uprising of Office 365 adoption and the limited options to migrate data natively between tenants.

The problem doesn’t stop there. These are vast and thorny projects which require a lot of planning, accuracy and time. Sometimes without warning, one seemingly small problem can turn into huge disruption to your environment. One of these issues which is particularly prominent is Mailbox Permissions. In this article, we’ll take a dive into what Sigi and Mike chatted about in this week’s episode of the Practical 365 Podcast.

Why is it so hard to Migrate Exchange Mailbox Permissions?

In the podcast, Mike highlights that Migrating Mailbox Permissions will be an area in your project which hosts the most complexity. Larger organizations often struggle with the full mailbox permissions, delegates and folder permissions. And a lot of the big questions raised are surrounding what should we migrate? Whether this is shared mailboxes, user mailboxes or room accounts. This also often depends on the company, what their usage is and how long Exchange has been in use.

Below are guides which can help you combat these problematic areas: 

If you forget about folder permissions during a mailbox migration, there are many things which can go wrong. A prime example is you can have a successful weekend migration, however, on Monday morning you may come back to mayhem. You’ll see your helpdesk volume would have substantially increased, your users will have forgotten how to set this up and use it. It also breaks business process and sometimes can create data security issues with over sharing.

Other areas you should look out for during migrations are ‘stale permissions’, also closely related are ‘automap’ stale permissions. You should also be weary of domain moves and timing or applying the permissions.

If you’re about to embark on an Office 365 tenant to tenant migration and would like to learn more about any of the issues discussed in this article, you can attend Mike’s upcoming webinar:

 Office 365 Tenant Migration:
How to Migrate Exchange Mailbox Permissions


About the Author

Siegfried Jagott

Siegfried is a Microsoft MVP for Office Apps and Services. He has great expertise in Office 365 implementations with a special focus on Security, Messaging and Identity for international customers.

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