Version 3.4
Updated 3.1.2026

Overview 

This master handbook combines the Gold‑Standard Migration Guide, Support KB procedures, architecture diagrams, migration workflow, migration checklist, and troubleshooting decision trees for Add2Exchange Enterprise hybrid migrations.

If you are currently syncing on premises, you will need an Add2Exchange Enterprise Edition 365 module upgrade license.  Please contact softwaresupport@diditbetter.com.

Microsoft References

Install Azure AD Connect
https://learn.microsoft.com/en-us/azure/active-directory/hybrid/how-to-connect-install-express

Hybrid Public Folder Documentation:
Enable the MRS Proxy endpoint for remote moves | Microsoft Learn
https://docs.microsoft.com/en-us/exchange/collaboration-exo/public-folders/set-up-modern-hybrid-public-folders

Legacy Hybrid Public Folders:
https://docs.microsoft.com/en-us/exchange/collaboration/public-folders/set-up-legacy-hybrid-public-folders

Hybrid Deployment Overview
https://learn.microsoft.com/en-us/exchange/hybrid-deployment/hybrid-deployment

Hybrid Deployment Prerequisites
https://learn.microsoft.com/en-us/exchange/hybrid-deployment/prerequisites

Hybrid Configuration Wizard
https://learn.microsoft.com/en-us/exchange/hybrid-deployment/hybrid-configuration-wizard

Move Mailboxes Using Hybrid Migration
https://learn.microsoft.com/en-us/exchange/mailbox-migration/move-mailboxes-using-hybrid-migration

Migrate Mailboxes Using Exchange Admin Center
https://learn.microsoft.com/en-us/exchange/mailbox-migration/migrate-mailboxes

Create Migration Batches
https://learn.microsoft.com/en-us/exchange/mailbox-migration/create-migration-batches

Azure AD Connect Overview
https://learn.microsoft.com/en-us/azure/active-directory/hybrid/whatis-azure-ad-connect

Directory Sync Scheduler
https://learn.microsoft.com/en-us/azure/active-directory/hybrid/how-to-connect-sync-feature-scheduler

Modern Hybrid Public Folders
https://learn.microsoft.com/en-us/exchange/collaboration-exo/public-folders/set-up-modern-hybrid-public-folders

Legacy Hybrid Public Folders
https://learn.microsoft.com/en-us/exchange/collaboration/public-folders/set-up-legacy-hybrid-public-folders

Autodiscover Service
https://learn.microsoft.com/en-us/exchange/architecture/client-access/autodiscover

Hybrid Deployment Best Practices
https://learn.microsoft.com/en-us/exchange/hybrid-deployment/best-practices

Architecture Overview

Typical hybrid deployments include Active Directory, Entra AD Connect synchronization, Exchange Online, and an Add2Exchange replication server, with the replication server either on premises, joined to the domain or unjoined, or hosted.

Proof of Concept Migration (Test Batch) Add2Exchange Enterprise synced objects Migration, Deployment, and Support Guide

This technical bulletin provides the definitive reference for migrating environments from on‑premises Microsoft Exchange to Office 365 in hybrid mode.

Core Migration Principles

Successful Add2Exchange hybrid migrations follow several core principles:

Synchronization stability must be maintained throughout the migration. No dereplication is required or desired.  Active content updates should be maintained throughout the migration.

Directory synchronization must be verified before mailbox migration begins.
Service account permissions must be validated before automation scripts run.
Mailboxes should be migrated in controlled batches.
Service accounts and shared resources should be migrated last.

Supported Migration Scenarios
The following scenarios are supported:

• Exchange On‑Premises → Microsoft 365 migration
• Hybrid coexistence environments
• Public folder hybrid environments
• Cross‑domain migrations (with extra processing)
• Swing or Staged mailbox migrations
• Resource mailbox replication

Architectural Overview
Typical architecture components:

Active Directory → On‑Prem Exchange  ↘ Add2Exchange Replication Server
↘ Azure AD Connect → Azure Active Directory → Exchange Online
On‑Prem Exchange Server or Hosted Exchange Server (this process may not work in Hosted Exchange without setting up Entra AD Connect)

Active Directory with user account outside system with Domain Administrator rights
Entra AD Connect (DirSync)
Entra Active Directory
Exchange Online
Add2Exchange Replication Server with synchronization Service Account and credentials

Current On‑Prem permissions -Typical deployment
The Default Synchronization Service account: zadd2exchange (yours may be different)

:• Domain User
• Local Administrator on replication server
• Exchange Organizational Administrator

Required (Highly Recommended) Microsoft 365 permissions:
• Exchange Administrator Role (or use another account when onboarding)

Ensure the following SIDS are synchronized:
• Service account
• Managed distribution lists
• Source mailboxes
• Destination mailboxes

Recommended settings:
• OU Sync Enabled
• SID Sync enabled

Migration Flowchart

 

Migration Checklist

✔ Azure AD Connect operational
✔ SIDS for relevant objects synced from on prem to Entra
✔ Hybrid Exchange configured
✔ Replication server patched
✔ MRS Public Folder Proxy setup (if applicable) Enable the MRS Proxy endpoint for remote moves | Microsoft Learn

✔ Users and Distribution lists SIDS synchronized
✔ Service account permissions in O365 validated
✔ Test mailbox ready for Proof‑of‑Concept
✔ DNS and Autodiscover verified

Recommended settings:
• OU filtering enabled
• Password hash synchronization
• Automatic synchronization cycle enabled

Directory Sync Validation:
✔ Service account SID synchronized, licensed and Roles assigned
✔ Distribution lists synchronized
✔ Mailbox objects synchronized
✔ Security identifiers synchronized

Migration Best Practices
Recommended migration order for smooth transition using Exchange Migration tools:
1. Distribution lists
2. All Synced Standard user mailboxes
3. Then Service account
4. Then Source resources
5. And if applicable: Public folders

Migration Workflow
The following flowchart summarizes the recommended migration workflow.

Mailbox Migration Procedure
Step 1: Stop the Add2Exchange Service and turn off Relman timer.
Step 2: Open Exchange Admin Center → Mailboxes → Migration → Migrate to Exchange Online.
Step 3: Create a migration batch and select users.
Step 4: Start the migration batch.
Step 5: After migration completes run the scheduled task 'A2E Dual O365 Permissions to All’.
Step 6: Wait 15 minutes
Step 7: G type migration: Open A2E Console to evaluate all dist. lists for new IDs and apply
                Confirm ALL Templates
Step 8: Close Console Restart the Add2Exchange service.
Step 9: Turn on Relationship Manager to previous timer interval (default 6 hours).
Step 10: Review the logs

Support Escalation
If synchronization issues persist after verifying service status, permissions, and directory synchronization, contact DidITBetter Premier Support or your dedicated support engineer.

Synchronizing environments to Microsoft 365 while maintaining synchronization using Add2Exchange Enterprise Edition (A2E) usually requires support.  During hours and After-hours support is available at 813-977-5739 or 813-927-3804.   This assistance can ensure stable synchronization, proper permission automation, and minimal downtime.

Proof of Concept or Live Migration Overview

Prerequisites to Setup a test: Add test user to our managed Distribution list.

1. Apply permissions and validate permissions.
2. Let it sync to the test user by running synchronization.
3. Validate replication
    

Start Test Migration

1. Stop Add2Exchange Service
2. Open Exchange Admin Center Mailboxes → Migration → Migrate to Exchange Online
3. Create Migration Batch
4. Select test users to migrate.
5. Start Migration Batch
6. Once done, Run Permissions Script: Either run the scheduled task: A2E Dual O365 Permissions to All or manually through the Auto Logon Shell in the DidITBetter Support Menu.ps1
7. Wait 15 minutes for permission to apply.
8. Seed the source with a new temp appointment or contact
9. Restart Add2Exchange Service
10. Review Logs

Migration Best Practices
Recommended migration order:
1. Standard user mailboxes AND Distribution lists
2. Usually LATER, after the migration of all mailboxes,then the Service account is migrated
3. Migrate Source resources and Public folders if applicable or left on Premises

Troubleshooting Decision Tree

Migration - Not Syncing new seeded object.

├─ Is A2E Service Running?

│     ├─ No → Start Service

│     └─ Yes

├─ Were Permissions Applied?

│     ├─ No → Run Permissions Script

│     └─ Yes

├─ Did DirSync Complete and user can be seen in O365?

│     ├─ No → Force Azure AD Sync and wait 15 minutes, then run Permissions Script

│     └─ Yes

└─ Review Add2Exchange Logs

Recovery Procedures

If synchronization fails:

1. Stop Add2Exchange service
2. Verify DirSync completion
3. Reapply permissions and wait to propagate fully
4. Validate distribution lists and migrated user is in O365

Post‑Migration Validation

✔ Add2Exchange logs clean
✔ Folder permissions correct
✔ Distribution list membership accurate
✔ Synchronization cycles successful

Onboarding Users in the Synchronization
The process is the same as it was when Stores were on premises but may take longer due to Entra Directory sync and permissions propagation delays.

1. Create AD object
2. Place in synced OU
3. Create mailbox in Microsoft 365
4. Assign license
5. Add to distribution list
6. Run permissions manually or automatically with the permissions PowerShell

Offboarding Users in the Synchronization
1. Remove from distribution list
2. Wait 24 hours
3. Then you can Archive, remove license, convert to shared mailbox or delete mailbox

Live Exchange Mailbox Migrations – Use the same process for testing Proof of Concept existing users and Live Migration

This is the procedure for keeping Add2Exchange working on cloud hosted/migrated mailboxes.

Stop Add2Exchange Service

1. Log into Add2Exchange server.
2. Stop service “Add2Exchange”.

Migrate Mailboxes

1. Go to Office 365 Admin – Exchange.
2. Click on “Mailboxes”.
3. Click on “Migration”.
4. Choose “Migrate to Exchange Online”.

5. Leave on defaults for New Migration batch. Next.

6. Click the + button and select user you want to move. Next.

7. Confirm migration endpoint. Next.

8. Name new migration batch. Next.
   1. Note the user must have your group.mail.onmicrosoft.com email address on their hosted mailbox prior to migration (Ex: connetts@yourgroup.mail.onmicrosoft.com)

9. Leave defaults. Next.

10. Click on New and the migration will start. Length will be determined by size of mailbox; it could take hours. When it is done migrating, you will get an email confirmation, and you must log in to complete the migration process.
11. Once migrated, finalize and assign a license.
12. Log into Add2Exchange server.
13. Run Permissions Task - Run scheduled task “A2E Dual O365 Permissions to Distribution List” on demand.
14. Wait 15 minutes for the permissions to propagate.
15. Open the Add2Exchange Console, select Relationship Group Manager (RGM) and select every distribution list and let it evaluate and press Apply.
16. Confirm the Templates with folder update selected.
17. Start Add2Exchange Service
18. Review Event logs.
19. Once all users are migrated, you can migrate the service account and license.
    1. Stop the Add2Exchange Service
    2. Migrate the Sync Service account.
    3. Assign License if not done already.
    4. Open Outlook to reconfigure.
20. Either Leave the Public folders on premises or migrate them
    1. If migrating public folders and resources, Stop the Add2Exchange Service
    2. Migrate the Public folders with Exchange Migration Tool and finalize.
    3. Open Outlook to reconfigure.
    4. Open the Add2Exchange Enterprise Console and Confirm all Templates.
    5. Relicense to O365
    6. Close Console and start synchronization.

 

End of Migration process