Step 1: Assess and Plan Migration Scope
Inventory every public folder being migrated, including size and item count. If the scope exceeds 1,000 folders including subfolders, or 20GB of data, contact BitTitan Support before starting. Public folders with more than 100,000 items need to be split into multiple folders before migration runs.
Step 2: Verify Exchange Web Services
EWS must be active on both source and destination environments. Microsoft has announced EWS blocking begins October 1, 2026. Confirm this is enabled before any other configuration work starts.
Step 3: Prepare the Exchange Environment
Grant the migration administrator account root-level access to all public folders with at minimum Reviewer permissions. Confirm the administrator account has an active mailbox on the Exchange server hosting the source public folder database. For Hosted Exchange environments, ask the provider to run a PowerShell script to retrieve the PublicFolderRootEntryId.
Step 4: Create M365 Accounts and Configure the Primary Hierarchy Mailbox
Create M365 accounts with the appropriate licenses for all users. In the M365 Admin Center, create the first public folder mailbox, which becomes the primary hierarchy mailbox in the destination tenant. Assign Full Access permissions on that mailbox to the destination administrator account.
Step 5: Set Public Folder Quotas to Unlimited
M365 defaults public folder quotas to 2GB with a warning at 1.7GB. That ceiling is too low for migration. Raise the quota to unlimited using PowerShell or the Exchange management portal before migration runs. Leaving this at default causes failures mid-migration that require intervention to resolve.
Step 6: Pre-Allocate Mail Folders for Large Migrations
If migrating more than 20GB, contact BitTitan Support before starting. They will generate PowerShell scripts that pre-allocate mail folders correctly. M365 cannot auto-split during migration, and if it attempts to, the process can take up to two weeks and will block access to all affected public folders during that time.
Step 7: Create the MigrationWiz Project
Log in to MigrationWiz. Select Public Folder as the migration type. Name the project, select the client, and save before moving to endpoint configuration.
Step 8: Configure Source and Destination Endpoints
Set the source endpoint to your Exchange environment, either On-Premises Exchange 2007 or later, or Hosted Exchange. Set the destination endpoint to M365 Public Folders. For M365 endpoints, complete the client ID and tenant ID fields before saving.
Step 9: Add Public Folders to the Migration Project
Enter the public folders being migrated in the Root Folder Path field. Using a forward slash migrates all public folders from the root down. Verify the path before running any migration pass.
Step 10: Export SMTP Addresses for Mail-Enabled Public Folders
Run the provided export scripts to generate a CSV of SMTP addresses for all mail-enabled public folders. MigrationWiz cannot migrate SMTP addresses for mail-enabled folders automatically. They must be exported now and imported separately after migration completes.
Step 11: Run a Credential Verification Pass
Before running any migration, perform a credential verification pass to confirm both source and destination endpoints are configured correctly and accessible. Resolve any failures here before proceeding.
Step 12: Configure Advanced Settings
Set any advanced options the migration requires. Date and item filtering, folder mapping, and other customizations should be configured and documented before the first migration pass runs.
Step 13: Run the Initial Migration Pass
Execute the initial migration pass to transfer public folder data, permissions, and associated content including emails, contacts, and calendars from source to destination. Document the results before running subsequent passes.
Step 14: Run Additional Migration Passes
Run two to three additional passes to capture changes made since the initial pass and confirm all security group permissions have migrated correctly. Each pass should be documented and reviewed before the next one runs.
Step 15: Configure Mail Flow for Mail-Enabled Folders
Review mail routing configuration and confirm that messages sent to mail-enabled folders are reaching the correct destinations. Import the SMTP addresses exported in Step 10 using the provided import script.
Step 16: Complete Post-Migration Activities
Give users access to the migrated public folders. Validate folder permissions against the pre-migration baseline. Communicate any changes to affected users before they encounter them. Monitor the source environment and decommission it only after migration is confirmed complete and stable.
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