Office 365 Public Folder to Shared Mailbox Migration

This guide explains how to migrate supported content from selected Office 365 / Microsoft 365 Public Folders to prepared destination Shared Mailboxes. Public Folders and Shared Mailboxes are different Microsoft 365 workloads: this process migrates supported content and does not convert the Public Folder object or automatically transfer its workload-specific configuration.

Organizations may use this scenario when shared Public Folder content is better managed in destination Shared Mailboxes. Prepare each target Shared Mailbox and its required access before mapping. Destination delegation, retention, compliance, and other mailbox settings should be configured or validated separately according to organizational requirements.

EdbMails Office 365 migration software supports this workflow with OAuth 2.0 / modern authentication, Public Folder selection, source-to-target mapping, selective migration, incremental repeat runs, and migration reports. Mapping associates selected source content with an existing/prepared destination Shared Mailbox; it is not Shared Mailbox provisioning.

The six-step workflow below covers preparation, source Public Folder connection and selection, target Shared Mailbox connection, mapping, migration, monitoring, and destination validation.

Use migration logs together with destination checks to validate supported migrated content. Microsoft 365 service limits, mailbox capacity and licensing, network conditions, and throttling can affect migration planning and performance.

1. Office 365 Public folder to Shared mailbox : Pre-migration Activities

   1. Ensure that you have a global admin account for the automatic registration method to connect to the source and target Office 365 servers.
   2. Ensure that you meet the network and bandwidth requirements for the migration. See network and migration planning, performance factors and best practices for Office 365 Public migration
   3. Prepare your target Office 365 tenant. See tenant roadmap for Microsoft 365.
   4. Ensure to set admin permissions for source public folders
   5. Analyze the Public Folder hierarchy before migration and identify inactive or obsolete folders that are no longer required. Cleaning up unnecessary content before migration can reduce migration time, improve performance, and simplify the organisation of Shared Mailboxes after migration.
   6. Create Shared mailboxes on the target Office 365 tenant and set the required permissions
   7. If this migration is part of a broader tenant/domain cutover, add and verify the required custom domain on the target Microsoft 365 tenant according to your cutover plan. A domain change is not inherent to every Public Folder-to-Shared Mailbox migration.
   8. Review current Microsoft 365 message/item limits and destination mailbox capacity for the selected content before migration. Do not assume the migration removes Microsoft service limits.

2. Steps to migrate Office 365 Public folder to Shared mailbox

   Step 1: Download and install EdbMails Office 365 migration software

   • Download EdbMails and install the application on any computer.

       See a detailed list of EdbMails system requirements for Office 365 migration.

   • Launch the application and click ‘Login’ or ‘Start Your Free Trial’

     

   • Select the ‘Office 365 Migration’ operation

     

   • Choose the ‘Office 365 to Office 365 Migration’ option.

     

   • Keep the default job name, or click ‘New Job’ to change.

     

   Step 2: Connect to the source Office 365 server

   • To set up a new connection to the source Office 365, click the ‘Add New Connection’ button. If you prefer using a previously established connection, simply choose it from the list and click ‘Connect to Existing’ to continue.

     

   • Select ‘Connect to Public Folders’ and then click ‘Next’ to continue.

     

   • Select one of the methods for secure OAuth 2.0 authentication and click ‘Login’ to continue.

     

   • For the automatic registration method, sign in on the Microsoft authentication page using a Global Administrator account. Use the documented credentials/permissions for the authentication method you select.

     

   • After successful authentication, choose a method to load the public folders and click ‘Next’ to continue.

     

   Step 3: Select Public folders

   • Select the public folders you wish to migrate and click ‘Next’ to establish the connection with the target server.

     

     Tip: If this is the first time you’re migrating with EdbMails, the migration is a full migration. On subsequent migrations from the same source to the target, the migration is incremental.

   Step 4: Connect to target Office 365 server

   • Click ‘Add New Connection’ to set up a new connection to the target Office 365 account. To use an existing connection, select it from the list and click ‘Connect to Existing’ to continue.

     

   • Select ‘Connect to Primary / Shared Mailboxes’ option.

     

   • Select the authentication method.
   • Click the ‘Login’ button to continue and authenticate with Microsoft sign-in page

     

   • Choose a method to load the shared mailboxes. You can also load the shared mailboxes using CSV file

      See how to load mailbox / shared mailboxes using a CSV file.

     

   Step 5: Map Public folder to Shared mailboxes

   • Before mapping, ensure to create shared mailboxes on your target Office 365 servers and assign the required permissions. Choose the required option to map your public folder to shared mailboxes

     

      Click here to know about user-defined mailboxes / folders mapping

   • Map your source public folder to the required shared mailboxes on the target server.

     

   Step 6: Start Office 365 public folder to Shared mailbox migration

   • After completing the mapping, click the ‘Start Migration’ button to initiate the migration process.

     

   • Once the migration is complete, a message will appear to review the migration status. Click the ‘View Log’ button to check the migration report. Log in to your target server to verify the migrated items.

     

3. Office 365 public folder to Shared mailbox post-migration validation

   • Step 1: Review migration status and reports

     Review the EdbMails migration status and logs, then inspect the destination Shared Mailbox folders and selected migrated items.

   • Step 2: Validate destination access and delegation

     Confirm that intended users can access the destination Shared Mailbox. Configure and validate Full Access, Send As, Send on Behalf, and other delegation separately where your organization requires them; source Public Folder permissions should not be assumed to transfer.

   • Step 3: Review destination retention and compliance

     Review any required Microsoft 365 retention, hold, eDiscovery, compliance, and mailbox-policy configuration separately. Migrating content does not automatically recreate Public Folder-specific policies or compliance configuration.

   • Step 4: Apply broader cutover changes only when applicable

     MX, Autodiscover, Outlook-profile, domain, subscription, or source-tenant decommissioning changes are relevant only when this Public Folder migration is part of a wider tenant or domain cutover. Do not remove the source subscription or domain solely because this migration job has completed.

4. Assess Public Folder Size and Shared Mailbox Capacity

   Review the size of the source Public Folders and ensure each destination Shared Mailbox has sufficient capacity before migration. Microsoft states that an unlicensed shared mailbox is limited to 50 GB; larger capacity, archiving, and some advanced compliance/security scenarios require appropriate licensing. Users who access a Shared Mailbox also require appropriate licensed access. Verify current Microsoft 365 quotas and licensing for your scenario.

5. Office 365 public folder to Shared mailbox migration troubleshooting

    See Office 365 migration troubleshooting guide and Public folder troubleshooting for possible solutions related to migration errors. For more information on EdbMails Office 365  migration, see frequently asked questions (FAQs)

    See solutions if you are not able to migrate Public folders due to insufficient permissions.

6. Post-Migration Validation Checklist

   After the migration is completed, verify the following:

   • Review migration logs and status for the selected Public Folders.
   • Inspect destination folders and compare representative item counts and selected migrated items with the source.
   • Verify that supported migrated emails, calendar/contact items, attachments, and applicable item properties are accessible in the destination.
   • Confirm destination Shared Mailbox access and configure required delegation separately.
   • Review destination retention, hold, eDiscovery, compliance, and mailbox-policy settings separately where required.
   • Investigate reported migration errors or skipped items before completing the project.

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Additional resources:

• Office 365 migration software
• Office 365 archive mailbox to Exchange guide
• Office 365 public folder migration to Office 365 guide
• Office 365 public folder to Exchange guide
• Office 365 migration to PST guide