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. This document will walk you through the environment preparation and MigrationWiz steps necessary to perform your migration.

  We recommend reading through the complete guide before starting the migration to understand the process, timeline, and prerequisites. You will see notes called out throughout the guide; pay attention to these, as they may provide information to avoid migration failure.

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

 BitTitan support does not offer post-migration guidance regarding the management and resolution of public folders on the source environment.


 MigrationWiz is a migration tool, not a syncing tool. If changes are made at the source after migration, they will not sync to the destination, nor will changes made at the destination sync to the source. We do not have “live” monitoring of changes (as with a sync agent) and we cannot handle scenarios such as conflict resolution without user interaction.

 MigrationWiz supports the capability to share migration projects across a Workgroup. When the Project Sharing feature is turned on, all Agents besides those who are Inactive can view all migration projects. For more information, visit Project Sharing in MigrationWiz.


Please consider the information below before choosing this migration type.


Purchase Public Folder licensesTo 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.

Purchase licenses Considerations

Purchase licenses by following the steps below.

  1. Sign in to your BitTitan account. 
  2. In the top navigation bar, click Purchase.
  3. Click the Select button and choose the license type you need.
  4. Enter the number of licenses you want to purchase. Click Buy Now.
  5. Enter a Billing address if applicable.
  6. Click Next.
  7. Review the Order Summary and enter a payment method.
  8. Click Place Your Order.


  • We are not able to support migrations with two-factor or multifactor authentication. 
  • Exchange Web Services (EWS) must be enabled in both the source and destination for this migration type.
  • Shared mailboxes require delegated permissions for access to folders. Currently, MigrationWiz does not update the source Public Folder permissions to the destination Shared Mailbox delegated permissions. Our development team is working on the fix, until then the destination Shared Mailbox delegate permissions need to be applied manually.

Migrated Items

What items are and are not migrated?

Public Folders can only be migrated to other public folders or shared mailboxes. We do not migrate Public Folders to individual user mailboxes or Microsoft 365 Group mailboxes or vice versa. Mail-enabled public folders are not supported for destination endpoints that are Exchange On-Premise and will need to be mail-enabled manually. For additional details about items that are and are not migrated from public folders, see our Migrated and Not Migrated Items article.

Exchange 2010 SP1+ & Microsoft 365


  • Public Folders and Subfolders
    • Mail Folders
    • Calendar Folders
    • Contact Folders
    • Tasks
    • Notes
    • Journals
  • User Permissions (Folder level only)
  • Mail-Enabled Security Group Permissions (Default and Anonymous User Permissions are not supported) - Folder level only

Not Migrated

  • Rules

Not Migrated in any Exchange Instance

  • Email templates
  • Email flags (if the destination is G Suite)
  • Safe Sender/Block Lists
  • Mail Settings
  • Standalone documents stored in Mailbox Folders or Public Folders (Example: IPM.Document item types)
  • System Public Folders
  • StickyNote folders
  • Delegated permissions

Not Migrated in Exchange 2007: Public Folder Permissions

Modern Authentication Requirements

The steps listed in the Obtain Client and Tenant ID Settings for Mailbox and Exchange Online Migrations section of the Authentication Methods Migrations KB apply to both the source and destination tenant when they are Exchange Online, in regards to Exchange Web Services (EWS) in mailbox, archive mailbox, and public folder projects. Use a Global Administrator for the configuration steps.

Please review the documentation before preparing the environment.

Prepare the Source Environment

  1. Grant admin permissions
  2. Break up large folders (if required)

Grant admin permissions

Break up Large Folders

You will want to perform these tasks first before beginning your migration. If you are migrating more than 1,000 folders (including subfolders) and/or more than 20GB of data, break these folders up before contacting BitTitan Support.

  • Split up large Public Folders: if any source Public Folders contain more than 100,000 items (if Source = O365, Exchange 2010 or later), these should be split into multiple Public Folders as they can cause migrations to be held up with processing of the high number of items. Breaking up these folders can help with faster migration speeds. For more information, see Finding Public Folder Size for Migration
  • Any individual Public Folders that are over 20GB in size should be split up into smaller folders of 20GB or less. Failure to complete this step can negatively impact migration performance and speed.

Prepare the 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.

Increase message size limits

Increase the public folder quotas to Unlimited. The default Microsoft 365 Public Folder quota setting is 2GB, with the issue warning set to 1.7 GB. These steps are from our article Microsoft 365 Public Folder Migration FAQ.

  1. Open a PowerShell session and enter the following. Then press Enter:
    $LiveCred = Get-Credential
    Install-Module -Name ExchangeOnlineManagement
    Import-Module -Name ExchangeOnlineManagement
    Connect-ExchangeOnline -ConnectionUri -Credential $LiveCred
  2. Enter the following command and press Enter. This will show you the current limits set on the public folder mailboxes:
    Get-Mailbox -PublicFolder | fl Name,MaxSendSize,MaxSendSize
  3. Enter the following command and press Enter. This will increase the MaxSendSize and MaxReceiveSize to the maximum allowed limits. (If there are items at the source that are larger than 150 MB, they will not migrate.)
    Get-Mailbox -PublicFolder | Set-Mailbox -PublicFolder -MaxReceiveSize 150MB -MaxSendSize 150MBAdditional details about send and receive size limits can be found in our Best Practices for Migrating On-Premises Exchange Public Folders article.

MigrationWiz Steps

The following steps will be performed in MigrationWiz.

  1. Create project.
  2. Set endpoints.
  3. Add items.
  4. Run Verify Credentials.
  5. Set Advanced Options.
1. Create project 2. Set endpoints 3. Add items 4. Run Verify Credentials

Create a Public Folder migration project. Read the MigrationWiz Projects article for more information on project types and troubleshooting.

  1. Click the Go to My Projects button.
  2. Click the Create Project button.
  3. Select Public Folder as the migration type.
  4. Click Next Step.
  5. Enter a Project name and select a Customer.
  6. Click Next Step.

Set Advanced Options


The advanced option steps listed below should be followed in the order that they are entered as they are required for this migration scenario.

Support Tab

  • RemoveFilterBasedOnFolderType=1 This support option is required if Public Folders contain items other than mail, such as calendar and contact items. This option stays in place for the entire migration process.
  • MustMigrateAllPermissions=1 This flag is required 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 Migrating Public Folders to Shared Mailboxes.
     Note: This option stays in place for the entire migration process.

Default Options for Microsoft 365 Endpoints

By default, some fields are view-only. In other words, you cannot edit or remove them from the support options page. To edit them, you need to edit the source or destination endpoint of your project.

Among these default options, you can find ModernAuthClientIdExport, ModernAuthTenantIdExport, ModernAuthClientIdImport, and ModernAuthTenantIdImport.

The support options above are required when configuring your endpoint.


You cannot update the default Advanced Options, in case you try to modify or add new ones the following message arises.
Duplicate Support Option.png

Performance Tab

  1. Set value for Licensing/Maximum licenses to consume per item per pass licensing count. Default = 1. This allows up to 10GB to be migrated. Example: If migrating all Public Folders, using the forward-slash ( / ), and the total data size = 78GB, then increase this value to 8 (otherwise the migration will pause at 10GB). See MigrationWiz Licenses.
  2. Set your Preferred BitTitan Data Center. For the most optimum migration speeds, select the Data Center that is closest to your Microsoft 365 destination tenant. Refer to MigrationWiz - General - FAQ.

Source/Destination Tab

  1. 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.
  2. Set the value for Migrate Permissions For from New Folders Only to New folders and existing folders

Run Migration

  1. 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.
  2. Perform the first pass for items older than 6 months by running a Full Migration. 
  3. Set second pass Project Advanced Options.
    • Set the Date Filter to migrate items newer than six (6) months. 
  4. Perform a second pass for items newer than 6 months by running a Full migration.
  5. 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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