Public Folder Migration Guide From On-Premises Exchange 2007+ to Microsoft 365 (Hybrid Mode)


This is the complete onboarding task flow for migrating Public Folders from On-Premises Exchange 2010 SP1 or later, to Public Folders on Microsoft 365, with a hybrid deployment. 

  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 does not migrate SMTP addresses for mail-enabled Public Folders. They can be exported and imported using the scripts supplied here: Migrating mail-enabled Public Folder email addresses. It is highly recommended to run the export script prior to migrating so you can ensure the csv file created contains the proper information. Do not run the import script until the pre-synced mail-enabled Public Folder contacts have been removed from Microsoft 365 (this is covered in the steps for mail-enabling the public folders near the end of this guide).

 Before beginning your migration, review the path mail flow takes for entering your environment when mail is sent to mail-enabled public folders, and to ensure the items will be delivered to the mail-enabled folders in Microsoft 365 once the migration is complete. MigrationWiz does not configure anything regarding mail flow, and assisting with mail flow issues is beyond the scope BitTitan support can assist with.

 Public Folder migrations can take some time to properly configure endpoints. We recommend configuring the project endpoints a week or more before the migration to ensure they are ready for use.


 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.

 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 

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 2007


  • Public Folders
  • Subfolders

Exchange 2010 SP1+ & Microsoft 365


  • Public Folders
  • Subfolders
  • User Permissions
  • Mail-Enabled Security Group Permissions (Default and Anonymous User Permissions are not supported)

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

Not Migrated in Exchange 2007: Public Folder Permissions

Special Considerations For This Migration

If your migration involves more than 1,000 public folders and/or more than 20GB of data, then there are additional steps that are required for a successful migration, and BitTitan Support will need to assist you. These steps are not required if your migration is smaller than that, and you may only require one or the other. Make sure you review these steps before beginning your migration.

Order of Operations

You must first successfully complete a Verify Credentials pass in your project before BitTitan Support can assist with these steps. Follow the steps starting at Prepare Source Environment through Run Verify Credentials below, then contact BitTitan Support. 

For Large Migration Projects

Open a ticket with BitTitan Support

Once you have completed the Run Verify Credentials step, open a ticket with BitTitan Support by following the instructions in How do I get support for your products? Make sure to include the following information in your ticket:

  • The subject of the ticket should be “Public Folder SPLIT or Mapping Scripts Needed”
  • Make sure to attach the folders.csv file to the ticket from the step above for migrating more than 1,000 folders if one is required.

If you have already submitted a ticket for another issue, simply add the new information to that existing ticket.

More than 1,000 folders (including sub-folders) More than 20GB of data

If migrating more than 1,000 folders in total (including sub-folders), the folders will need to be SPLIT into multiple line items in your MigrationWiz project. This process increases the efficiency of the migration in case there are specific folders that may cause issues during the migration, and to allow folders to be migrated in parallel line items instead of a single one. If you are migrating less than 1,000 folders for the project, this steps is not required.

    • First, run the following PowerShell command against your source Exchange server. This will generate a file called folders.csv that will be used to create the SPLIT project.
      Get-PublicFolder -Recurse -Resultsize Unlimited | select Identity | Export-Csv -Encoding Unicode C:\folders.csv
    • Once you have that CSV, follow these steps:
      • Open the folders.csv file and remove the folder paths for any folders that should not be included in the migration. After you have confirmed the folder paths listed in the folders.csv file are the ones to be migrated, save the file (do not change the encoding) and attach the file to the ticket and indicate this step has been completed. 
      • Once the folders.csv file has been used to create a secondary SPLIT project (it will have _SPLIT included in the name), this will be the project used to migrate your public folders moving forward.

SPLIT Folder Paths

Only folder paths present in the folders.csv file used to create the SPLIT project will be migrated. Any new folders added at the source after the creation of the SPLIT project will need to be manually added after. For suggestions on working within this restriction, see Best Practices for migrating Public Folders.

Modern Authentication Requirements

Exchange Online EWS Modern Authentication Requirements (click on this box to expand required steps)

The steps listed below apply to both the source and/or 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.


For setup steps that include images, see under Enabling Modern Authentication for EWS between MigrationWiz and your Exchange Online Tenant in the following KB: Authentication Methods for Microsoft 365 (All Products) Migrations

Important: Failure to perform the steps for your Microsoft 365 endpoints, can result in failed jobs with 401 errors like the following in your project: Http POST request to '' failed - 401 Unauthorized

The administrator account being used for the project needs to be excluded from any MFA/2FA policies or Conditional Access policies that can block access for the administrator account. This requirement does not apply to the items or users being migrated in the project.

Configuring Modern Authentication to work with MigrationWiz for mailbox, archive mailbox, and public folder projects in Exchange Online is now the default method after Microsoft discontinued support for Basic Authentication in Exchange Online after December 2022. The following Microsoft documentation outlines this change in more detail. Should you have additional questions on how this change may impact your tenant, please contact Microsoft to assist with providing that information: Deprecation of Basic authentication in Exchange Online

The Azure Security Defaults must also be disabled in the tenant. (This is often enabled by default for all new Exchange Online tenants and there is no workaround for this requirement). For steps on where to enable/disable the Azure Security Defaults, see Enabling security defaults in the following Microsoft documentation. To disable, set Enable Security defaults to No: Security defaults in Azure AD

Modern Authentication Steps
  • Log in to the Azure AD admin console with a Global Administrator login.
  • Select Azure Active Directory in the Azure Active Directory Admin Center.
  • Select App Registrations, which is found under Manage.
  • Select New Registration at the top of the screen.
  • Give the app a distinct name. You can change this later if necessary.
  • Select the Accounts in any organizational directory button.
  • Under Redirect Uri, select Public Client (mobile & desktop) and set it to urn:ietf:wg:oauth:2.0:oob
  • Click Register.
  • Go back to App registrations.
  • Select the App you just created.
  • In the Overview, you will find a ClientId (aka Application) and Directory (Tenant) ID.
  • Copy both of these to another application, such as Notepad, for use later in this process.
  • Under the Manage menu, select Authentication.
  • Set the option Allow public client flows to Yes
  • Click Save.
  • From the Manage menu, select API permissions.
  • If API permission named User.Read under Microsoft Graph is already present, this can be removed. The Microsoft Graph API is not applicable to this project type and is not used.
  • Select Add a Permission.
  • Select APIs my organization uses

  • Scroll down and select Office 365 Exchange Online

  • Then select Delegated Permissions

  • Select EWS

  • Check the box under EWS for EWS.AccessAsUser.All.
  • Click Add permissions. This permission only allows the OAuth application (MigrationWiz) to be associated with EWS.
      • Important: This does not grant access to all mailbox data.
  • Click Grant admin consent.
  • Click Yes to confirm the settings.
  • In MigrationWiz, select the project that needs to be configured for Modern Authentication.
  • Click the Edit Project menu.
  • Select Advanced Options.
  • Under Support Options enter the ClientID and TenantID information you saved earlier in the following format:
    • If enabling Modern Authentication for the Source:
      • ModernAuthClientIdExport=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
      • ModernAuthTenantIdExport=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
    • If enabling Modern Authentication for the Destination:
      • ModernAuthClientIdImport=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
      • ModernAuthTenantIdImport=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx 
        • Enter the specific ClientID and TenantID for your tenant in place of the xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.
        • These options can be entered for either the Source or the Destination, or both, depending on the settings on the tenants.
        • These options need to be configured for each MigrationWiz project that needs to have Modern Authentication enabled.

  • Run a Verify Credentials to confirm that MigrationWiz can connect using Modern Authentication. 
  • Click on the item that was verified. There will be a message in the MigrationWiz Migration Information page that Modern Authentication is being used. This message will show in the “Migration Errors” box; however, it is not an error. This is just a message confirming that Modern Authentication is now active and being used for the connection.

Prepare the Source

  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 sub folders) 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 Destination


This guide presumes that mail-enabled Public Folder email addresses have been synced between the source On-Premise Exchange server and Microsoft 365 with a script provided by Microsoft when setting up the Public Folder hybrid environment. These pre-synced, mail-enabled Public Folders will need to be removed from Microsoft 365 before MigrationWiz can be used to mail-enable the physically migrated Public Folders in Microsoft 365. The steps required for this are included in the MigrationWiz steps below. For more information, see Migrating Mail-Enabled Public Folders in Hybrid Mode.

This guide presumes that your Microsoft 365 tenant and users have already been created, and licenses have been assigned to enable the user mailboxes in Microsoft 365. If not, stop here and complete the Microsoft 365 setup as necessary, then continue with the following steps.

  1. Confirm the destination administrator account has a Microsoft 365 license and an active mailbox.
  2. Create the first Public Folder mailbox.
  3. Run PowerShell commands

Create public folder mailbox

Before giving Microsoft 365 users access to the On-Premise Public Folders, the first Public Folder mailbox in the Microsoft 365 tenant will need to be created. Do not name the primary mailbox the same as any public folder mailbox or database on the source On-Premise Exchange server. The following steps need to be used to create the first public folder mailbox correctly (this will be the Primary Hierarchy mailbox) in order to use MigrationWiz for this project type. It would be best to have your MigrationWiz project already created for testing. Those steps can be found below.

 This step is required regardless of migration project size.


If your tenant is currently set to remote for your public folders, these steps will break connectivity until the primary public folder mailbox has been created and confirmed as working correctly with MigrationWiz so you will want to plan a window to perform these steps. Expect a minimum of 1-6 hours. All PowerShell commands listed are to be run against the destination tenant.

  1. Ensure current remote settings are recorded by running the following Powershell command:

    Get-OrganizationConfig |fl *public*

  2. Run Set-OrganizationConfig -PublicFoldersEnabled Local -RemotePublicFolderMailboxes $Null

     This will break connectivity to the remote public folders for your users. You may wish to communicate this to them before running the command above.)

  3. Create the first public folder mailbox (this will become the primary). Don't name it the same as the remote mailbox on-premise.


    A maintenance window may be needed to reduce any downtime as access to the source On-Premise folders will be interrupted in order to create the Primary Hierarchy Public Folder.

  4. Once the first public folder mailbox is created, click on Public Folders and then ... . Add the destination administrator account being used in the project as Owner.
  5. Create a test public folder in the administrator UI where you just added the permissions.
  6. Set DefaultPublicFolderMailbox so that the destination administrator account mailbox being used is pointing at the newly created public folder mailbox in the destination tenant using the following PowerShell command:  Set-Mailbox –Identity –DefaultPublicFolderMailbox 365PFMBX

     Replace with the destination admin account being used and 365PFMBX with the name of the public folder mailbox you just created.

  7. If logged into Microsoft 365 with destination administrator account being used in project, then log out.
  8. After 15-30 mins, log back into Microsoft 365 with the destination admin account and open its OWA mailbox.
  9. Attempt to add the test folder created in step 5 as a favorite in OWA.This is done by right clicking on Favorites or Folders.

      If step 9 is successful, attempt to Verify Credentials in the public folder MigrationWiz project by selecting your line item and then select Verify Credentials from the Start Menu.

  10. If Verify Credentials is successful in project, then set the Get-OrganizationConfig back to the remote settings with the following commands and replace <YourOnPremisesPFMailbox> with the name you recorded from step 1. Set-OrganizationConfig -PublicFoldersEnabled Remote -RemotePublicFolderMailboxes <YourOnPremisesPFMailbox>

      This will return connectivity for the remote public folders on-premise for your users in Microsoft 365. There have been observed times as long as an hour before the setting takes full effect.

  11. Set DefaultPublicFolderMailbox for the destination administrator account mailbox back to the new primary public folder mailbox in Microsoft 365 using the same PowerShell commands used in step 7.

 You will need more than one public folder mailbox if migrating over 20 GB of data. See Large Migration Steps for more details.

PowerShell Commands

After all public folder mailboxes that are required for this migration have been created, you will want to increase the maximum send and receive limits, and increase the individual public folder size quotas for migration. Run the following PowerShell commands in the destination tenant:

Set-OrganizationConfig -DefaultPublicFolderProhibitPostQuota Unlimited -DefaultPublicFolderIssueWarningQuota Unlimited

Get-Mailbox -PublicFolder | Set-Mailbox -PublicFolder -MaxReceiveSize 150MB -MaxSendSize 150MB

MigrationWiz Steps

The following steps will be performed in MigrationWiz.

  1. Create project
  2. Create endpoints
  3. Add items
  4. Run Verify Credentials
  5. Purchase licenses
  6. 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.

Purchase licenses

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.

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.

  1. Under Source/Destination, set the value for Migrate Permissions For from New Folders Only to New folders and existing folders. This is required because Public Folder mapping scripts have been created. See Migrating Public Folder Permissions
  2. 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.
  3. 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.

Under Support Options add:

  • 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.
  • DoNotMailEnablePublicFolders=1 This support option is required and must remain until you are ready to mail-enable the migrated Public Folders after all folders, files and permissions have been migrated. This option must stay in place until you run the pass to mail-enable the migrated folders with step 3 under Mail Enabling Your Migrated Public Folders later in this guide.

Perform Migration

You will now begin your migration. This will occur in multiple phases. Each migration pass has additional required advanced options and will be submitted as a Full Migration. Each pass must be completed successfully before moving on to the next migration pass.

  1. First migration pass
  2. Second migration pass
  3. Security group permissions migration pass
  4. Mail-enabled public folders

The advanced options detailed in the migration steps in the tabs below are intended to help increase the speed of your migration. For additional details on these options, please view our FAQ article here.

1. First pass 2. Second pass 3. Permissions pass 4. Mail-enabled public folders

First Migration Pass Steps

The first migration for this scenario usually takes more time to complete than the subsequent passes, and completes the following tasks:

  • Folder and file/item discovery
  • Migrate user folder permissions if a match can be found. For more information on the requirements for migrating user permissions, see Migrating Public Folder Permissions

Additional advanced options

Set first pass Project Advanced Options (this is considered your pre-stage pass as the older items will be migrated first).

Under Support Options add:

      • MaintainWatermarkCompletionState=1 

Under Filtering:

      1. Select By Date
      2. Check box Only migrate items older than the specified date
      3. Set date range (month, day, hour, minute) for items to migrate. We suggest migrating items older than six months. Dates will be calculated by the most recent modification date.

Perform the first migration pass

      1. Perform first pass for items older than 6 months by running a Full Migration from the Start menu. 


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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