Exchange or Microsoft 365 Public Folder to Exchange or Microsoft 365 Shared Mailbox Migration Guide


This is the complete onboarding task flow for migrating public folders from Exchange 2007+ or Microsoft 365 to shared mailboxes in Exchange 2010+ or Microsoft 365.

Important: MigrationWiz is not a sync tool. Items updated at the Source will not be updated at the Destination. There is no process by which the calendars, contacts, tasks, etc., can be updated after being migrated.

Complete each step in the order listed. If additional instructions are required, a link to a corresponding Knowledge Base article is provided.

We are not able to support migrations with 2-factor or multifactor authentication. 

To see what items are included in the migration, see Which Items Are and Are Not Migrated by MigrationWiz?


Prepare Source Environment

  1. Create an administrator account in the source tenant to be used for migration or use the global admin account for the tenant. Read the Set Up Exchange Administrator Account article for more information. The administrator account must have a valid Microsoft 365 license assigned and an active mailbox. If migrating from Exchange 2007+, ensure that the administrator has an active mailbox enabled.
  2. Ensure that the migrating administrator account has permission on all Public Folders (owner access rights need to be permitted to the account being used for migration). Refer to Granting Necessary Permissions to Source Public Folders for more information.
  3. Split up large Public Folders (if any Public Folders contain more than 100,000 items, these should be split into multiple Public Folders. This will speed up your migration). Refer to Finding Public Folder Size for Migration for more information.

Prepare Destination Environment

  1. Use a global administrator account for the tenant. This can be an already created account or can be created specifically for this migration. The administrator account being used for the migration must have a licensed mailbox enabled in the tenant.
  2. Create the shared mailboxes and grant the destination administrator account Full Access permissions to the shared mailboxes. The steps to create these are defined in a TechNet article here.
  3. If the destination is Microsoft 365, increase the shared mailboxes maxsend and maxreceive size to 150MB. If the destination is Exchange, increase the message size limits. Refer to Increasing Maximum Received Message Size for details.


MigrationWiz Steps

  1. Set up the Public Folder migration project. If your Destination endpoint is GCC High, then select Office 365 (US Government) when creating your Destination endpoint.
  2. Set Project Advanced Options. 
    • Select the option for Migrate to: Shared Mailbox. This will be found under either Destination: Exchange Server 2007+ or Destination: Microsoft Office 365, depending on what was selected when creating the destination endpoint.
    • Under Source/Destination, set the value for Migrate Permissions For from "New Folders Only" to "New folders and existing folders". See Migrating Public Folder Permissions
    • Set value for Licensing/Maximum licenses to consume per item per pass licensing count. Default = 1 allows up to 10GB to be migrated, each additional license migrates up to 10GB more. Example: If migrating all Public Folders and the total data size = 78GB, then increase this value to 8 (otherwise the migration will pause at 10GB). See Multiple Licenses for a Single Item
    • Set your Preferred BitTitan Data Center. For fastest migration speeds, select the Data Center that is closest to your Microsoft 365 Destination tenant. 
    • Under Support Options add:
      • MustMigrateAllPermissions=1 This flag is required in order to migrate Public Folder permissions to a shared mailbox. This Advanced Option allows you to migrate all folder permissions, not only the system folders when migrating from Exchange 2010+ mailboxes as, by default, only systems folder permissions are migrated. We do not migrate Delegation, SendAs/SendOnBehalfOf permissions or any permissions for the Default or Anonymous user accounts. For more information, see Can I migrate Public Folders to Shared Mailboxes?
        Note: This option stays in place for the entire migration process.
  3. Purchase Public Folder licenses. To obtain an estimate of the number of Public Folder migration licenses required for your migration project, follow the directions in Estimating the Required Public Folder Migration License Count.
  4. Add source public folders and destination shared mailbox addresses to the project.
    • If migrating all public folders to a single shared mailbox, select Add > Quick Add and enter a forward slash ( / ) in the Root Folder Path field.
    • If migrating specific public folders to multiple shared mailboxes, select Add > Bulk Add and enter the full path of each source folder to be migrated in the Root Path field and the address of the intended destination shared mailbox in the Destination Email field.
    • If migrating to multiple shared mailboxes, open a ticket with Support using the Subject “Public Folders to Shared Mailboxes: License Audit”. Include the Project name, the total GB of source Public folder data to be migrated and the number of destination Shared Mailboxes being migrated to. This will allow Support to make sure that you have the correct number of licenses to migrate without having to purchase extras.
  5. Run Verify Credentials. For more information, see Verifying Mailbox Credentials Without Submitting Migration
  6. Set first pass Project Advanced Options. For more information on running multiple passes, see Pre-Stage vs. Big Bang Strategy for Public Folders.
    • Set Date Filter to migrate items older than six (6) months. Date range filters can be set under Advanced Options.
  7. Perform first pass for items older than 6 months by running a Full Migration. 
  8. Set second pass Project Advanced Options.
    • Set the Date Filter to migrate items newer than six (6) months. 
  9. Perform a second pass for items newer than 6 months by running a Full migration.
  10. Request the migration statistics. Click the bar chart icon on the MigrationWiz dashboard to receive an email containing all the project migration statistics. 
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