How to Migrate from Hosted Exchange to Exchange Online

How to Migrate from Hosted Exchange to Exchange Online


This article provides an example of how to migrate from the Atria Hosted Exchange Service to the Microsoft Online Service.  It will cover the change in service as well as data migration.  The process will use the following free Microsoft Migration guide:, however, a number of other migration products could also be used to migrate user data.  

In this example, we will be moving a set of existing Hosted Exchange users to Microsoft Online.  Our Example customer is Initech Software and we will be migrating all users.  As shown below the customer only has the Hosted Exchange service provisioned.  

Note: This guide will be using the Classic Exchange Admin Center, however, you can also use the modern option if it suits your use case.


  1. The steps provided in this guide assume that you already have the Microsoft Online Service provisioned and connected to your Microsoft Partner Center.  If you need to complete this step start at the following KB guide: 
  2. You should have a good working knowledge of Atria in regards to Customers, Users, and provisioning and de-provisioning of Services
  3. It also assumes you have DNS management of the Customer's public-facing domains.  Before we begin the migration we assume the domains will be configured for Exchange and pointing towards your Hosted Exchange environment.

Migration Steps

Step 1 - Provision Azure AD

Go to Customer Services and provision the Azure AD Service to the customer. 

If you are a Direct CSP (Tier 1) then you can create a new tenant if the customer does not already have one.  If you are Indirect (Tier 2) or the customer already has a tenant you can connect to their tenant provided it has been linked to your Partner Center account.  

If your customer has an existing tenant that is not yet linked to your Partner Center follow this guide: 

This customer does not currently have a Microsoft Tenant so we will create one by specifying a unique domain.

Note: The Set Target Address is required for this migration method, when the Set Target Address is set all emails sent to the recipient will unconditionally be forwarded to the mail address set in the attribute without delivering a copy to the user mailbox or sending it to group members.  This can be useful depending on your migration approach, consider carefully whether users will remain connected to their mailboxes or their new 365 mailboxes during migration and when domain cut-over will occur.  

Step 2 – Verify Customer Domain

As this is a new tenant, we need to verify the customer's public-facing domain.  Use the following guide for the various methods to do this 

If using the DNS TXT record method, when you enable the domain in Atria for Azure AD it will show the required TXT record to create, as shown below.

The Azure Portal will show that the domain has an incomplete setup.

Add the TXT record to your public DNS provider and complete the verification process in Office 365.

Once the domain is verified you can set the domain to be “Is Default” on the Azure AD service. 

Step 3 – Provision the Microsoft Online Service

Go to Customer Services and provision the Microsoft Online service to the Customer.  Select the Plans the that you want to offer to this customer.

Step 4 – Sync Azure AD

Go to the customer and select the Users or Services option to ensure you are connected to the correct customer.  Go to the main menu and select Services > Microsoft Online > Azure AD Sync

On the Azure AD Sync page select the option for Full Sync and click Sync Tenant.  This will create or match the users between the Atria AD and the customer Azure AD tenant. 

Note: double-check that the new domains have been applied to users correctly, it may be required to reprovision the customers and users if provisioning the next step (step 5) fails with a warning about setting the Target Address.  Confirm the users have their primary address set correctly.

Step 5 – Provision Microsoft Online to each user

Go to a user being migrated and select services.  Expand the Microsoft Online Service and Select the Plan you want to provision to the user.  For Multiple users, you can use the Multi User Select menu to assign the same plan.

Note: a temporary Azure AD password will be shown for the user.  Resetting the User's password in Atria will update both AD and Azure AD to be the same.

Repeat this step for each user.

Step 5 – Create a migration user

As part of the migration setup a user account is needed that has access to all mailboxes being migrated.  This can either be an existing user account you know the password of or an account that you have created.  In this example, we will create a user.

Create a new user account and assign it a mailbox and the Microsoft Online service the same as you did for existing users.

Step 6 - Assign the migration user full mailbox access right to each user's mailbox.

Go to a user > select services > expand Hosted Exchange > expand Advanced Options > Expand Mailbox Rights.
Tick the Full Access (Excluding Send As) Permission
In the member search box type in the Migration User name and click find
In the list select the user and click add

Click Close and Click Provision
Repeat for all users being migrated.  
Note: If you have a lot of users to update, contact us at for a script to help with this.

Step 7 – Set up the migration Endpoint

Logon to the customer's Office 365 Tenant
On the left side menu go to Admin Centers > Exchange
In the Exchange Admin Center go to the bottom menu and select Exchange Classic
Go to recipients and migration

Click on the 3 horizontal dots and select the option to add an Endpoint

Click on the plus symbol to add a new Endpoint, a wizard will start  

For the Migration Type Select Outlook Anywhere

On the next window specify an email address of a user being migrated. 

Then provide the account details for the migration user.  Use domain\username format.

If your Exchange environment is set up correctly it will auto-populate these next settings.
If they don't appear provide the internal server name and RPC proxy typically the externally resolvable address for the Exchange Server.

Provide a name for the Migration Endpoint.
Set the maximum concurrent migration settings, note: too high a value may have a performance impact on your Exchange Server.

Click New to finalize the Endpoint setup.

Step 8 - Start a new Migration Batch

Click the plus symbol and select migrate to Exchange Online
Choose the option for Cutover Migration

The Migration Endpoint will already be selected, click next

Name the migration and click next

Select a time for the migration to start or select to start Automatically

Once the migration starts there will be a status of Syncing.  All mailboxes that the Migration User has access to will be migrated.

When the migration has completed the status will change to Synced

Step 8 – Update DNS records to point to Hosted Exchange

In Office 365 go to Settings > Domains
Gather the additional settings for your domain to receive email directly and configure it with your domain provider.

Step 9 – Remove Migration Batch

In the Exchange Classic admin portal for the Customers Office 365 go to recipients > Migration and you can now delete the migration batch, you can also delete the migration endpoint.
Note: The finalized column is only used in Exchange Hybrid migration scenarios

Step 10 - Remove the migration user

If you used a dedicated migration user account you can now deprovision that user and associated services.

Step 11 – Deprovision Hosted Exchange from the customer

Once migration is complete and you have tested mail is flowing correctly to users in Office 365.  You can deprovision Hosted Exchange from the Users and Customer.

If there are any questions or assistance needed, feel free to contact

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