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Public Folder Migration Guide From On-Premises Exchange 2007+ to Office 365 > 20GB Hybrid mode

Last Update: 7/21/2017 11:34 AM
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​Important: When you sign in to MigrationWiz, you are redirected to the Getting Started page in MSPComplete. To get to a migration project created before April 4, 2017, click the Go to Projects button on the Getting Started Page. To create a new project for the migration scenario documented in this article, click the waffle icon (waffle.png) in the top navigation bar of MSPComplete, and select the appropriate migration product.


  • This guide should be followed if the total size of the Source Public Folders is more than 20GB. If the total size is less than 20GB, refer to KB005906.
  • Complete each step in order. If additional instructions are required, then a link to a corresponding Knowledge Base article is provided.
  • If you experience throttling limits when migrating to Office 365, and if you are migrating more than 1000 seats, you can increase throttling limits by following guidance provided in How to increase EWS throttling limits​. ​

Prepare Source Exchange Environment:

  • Set elevated 'Organization Management' admin role to migrating admin account (this grants permission to all necessary read-only fields). KB004788
  • Ensure migrating admin account has permission on all Public Folders (owner access rights need to be permitted to the account being used for migration). KB005103
  • Split up large Public Folders. If any Public Folders contain more than 20,000 items (if Source = Exchange 2007), or 100,000 items (if Source = Exchange 2010 or later), these should be split into multiple Public Folders. This will speed up your migration. KB005526

Prepare Destination Office 365 Environment:

  • Change Organization Configuration to use Public Folders on Office 365 (this step must be completed before any Public Folder mailboxes can be created on Office 365, when running in hybrid mode). KB005464
  • Create Public Folder mailbox, and assign root permissions to this Public Folder mailbox to the admin account being used for migration. KB005069 Video
  • Allocate public folders from the source to their corresponding public folder mailboxes on Office 365 such that each mailbox on the destination remains below 20GB
    • Note: This is important because public folders that are larger than 20GB can automatically trigger automatic splitting of the public folder mailboxes on Office 365, which may cause the migration to fail.
    • Important: If any public folders at the source are greater than 50GB, you must break these down into folders that are smaller than 20GB. To do this, you must work with BitTitan support to restructure your public folder hierarchy using PowerShell scripts provided by BitTitan. Click here to contact BitTitan Support​.
    • Note: This step can take several days to complete, so allow time for this in your project plan.
  • Revert Organization Configuration to remote, to restore the access to the On-Premises Public Folders (this restores access to the On-Premises Public Folders, for the Office 365 users). KB005464
  • Configure the admin account being used for migration, to look at Office 365 folders by default, while all other Office 365 users look at On-Premises Public Folders (this is required for migration). KB005102

MSPComplete Steps:

  • Create customer. KB005421
  • Create the Source and Destination endpoints. (Select Exchange Server Public Folder  for the source endpoint, and Office 365 for the destination endpoint.) KB005427
  • Launch public folder migration (select All Products > Public Folder Migration).

MigrationWiz Steps:

  • Set up Project (Create a Public Folder project/Name project and select the MSPComplete customer/Select the Source endpoint/Select the Destination endpoint).
  • Add Public Folders. To understand how pricing works, refer to KB004863.
  • Options:

    • Choose to migrate all Source Public Folders.
      • Select Add/Quick Add and enter a forward slash ( / ) within the field labeled Root Folder Path. KB004914
    • Use BitTitan AutoDiscover to discover all Public Folders on the Source, and then import them into your MigrationWiz dashboard. This allows you to pick and choose which Public Folders to migrate. Note: Each top-level folder will consume one Public Folder license. KB004915
      • Select Add/AutoDiscover items/Start Autodiscover/Import.
  • Run Verify Credentials. KB004511
  • If the Source Public Folders have more than 1000 folders below the top-level folder, work with BitTitan Support so that the migration can be split up, based on migration points after every 1000 folders. KB005239
  • Note: Once the tool is complete, you must run the migration from the new project, and can then delete the original project.

  • Purchase Public Folder licenses. KB004647
    • To obtain an estimate of the number of Public Folder migration licenses required for your migration project, follow the directions in KB005791.
  • Set Project Advanced Options. KB004834
    • Set the value for Migrate Permissions For to New folder and existing folders. This is required because Public Folder mapping scripts have been created. KB004817
    • 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, increase this value to 8 (otherwise the migration will pause at 10GB). If using AutoDiscover, and the largest top-level folder = 37GB, increase this value to 4. KB004890 KB004863
    • Add RemoveFilterBasedOnFolderType=1 under Support/Support options. This flag is required if Public Folders contain items other than mail, such as calendar and contact items. KB005053
    • Set Preferred BitTitan Data Center (for fastest migration speeds, select the Data Center that is closest to your Office 365 Destination tenant). KB004268
  • First Pass MigrationWiz Steps:
    • Set first pass Project Advanced Options: KB005067
      • Add: MaintainWatermarkCompletionState=1
      • Set date to migrate items older than six (6) months.
    • Perform Full Migration pass (checkmark the box next to Root Path, select the Start button/select Full Migration from the drop-down list/click on the Start Migration button).
  • Second Pass MigrationWiz Steps:
    • Set second pass Project Advanced Options: KB005067
      • Remove: MaintainWatermarkCompletionState=1
      • Add: SkipImportFolderWhenPublicFolderExists=1
      • Set the date to migrate items newer than six (6) months.
  • Perform Full Migration pass (put a checkmark in the box next to Root Path, select the Start button > select Full Migration from the drop-down list > click on the Start Migration button).
  • Perform a second Full Migration pass using the Advanced Option AllowAllMailboxTypesForPFPermissions=1 in order to migrate all Security Group Permissions. If you do not run the second pass, none of the Security Group Permissions will migrate.
  • Enable the Exchange online organization to access the Office 365 Public Folders. KB005090
  • Run DirSync, or Azure AD Connect (this synchronizes your On-Premises Exchange and Office 365 environments).
  • Mail-enable Office 365 Public Folders. MS TechNet article
  • Notes:

    • Change mail-enabled addresses for all Public Folders on Office 365 to be the vanity domain name, rather than the email domain name. Assign the pertinent SMTP email addresses to the mail-enabled Office 365 Public Folders using this Remote PowerShell command syntax:
    • set-MailPublicFolder -Identity PFAlias -PrimarySmtpAddress –emailaddresspolicy $false

    • When Exchange hybrid is in place, MigrationWiz cannot mail-enable Public Folders with the vanity domain name, because that address is already being used by the On-Premises Exchange 2013 mail-enabled Public Folders. Therefore, MigrationWiz defaults to mail-enabling the Office 365 Public Folders with email addresses using the "" email domain.
  • If necessary, configure some or all mail-enabled Office 365 Public Folders to accept mail from external domains, using these Remote PowerShell commands: KB005468
  • get-publicfolder -identity "\PFAlias" | Add-PublicFolderClientPermission -User Anonymous -AccessRights CreateItems


    get-publicfolder -recurse | Add-PublicFolderClientPermission -User Anonymous -AccessRights CreateItems

    Note: This step is important if external domains cannot send mail to the mail-enabled Public Folder email addresses.

  • Change your primary domain type in Office 365 from Authoritative to Internal Relay. KB005467
  • Note: Without setting this, Office 365 bounces the message before it even checks whether a valid Public Folder address exists.

  • Final Delta Pass MigrationWiz Steps:
    • Set final Delta pass Project Advanced Options: KB005067
      • Leave this flag as is: SkipImportFolderWhenPublicFolderExists=1
      • Set the date to migrate items newer than one (1) week.
    • Perform another Full Migration (Delta) pass. Put a checkmark in the box next to Root Path, select the Start button > select Full Migration (from the drop-down list) > click on the Start Migration button). KB004938
    • Note: This is important, in order to migrate any residual items that were sent to the Source Public Folders after the second migration pass began, when the Organization Configuration was set to remote, during migration.

  • Receive migration statistics (click on the pie chart on the MigrationWiz dashboard to receive an email containing all the project migration statistics). KB004626