1. Exchange to Microsoft Migration Overview

Furthermore, Cloudiway has developed a number of tools to enable seamless migration for the most intricate migrations. Our supplementary tools include:

  • Calendar Free/Busy display;
  • and, GALSync (Global Address Lists Synchronization).

To discuss any of these supplementary tools further, please get in touch with your existing Cloudiway contact.

2. Security

For more information about security, please refer to this article.

3. Performance

For more information about migration performance, please refer to this article.

4. Mail Migration Scope

5. Pre-migration configuration

5.1. Before you start

Before you start, you need the following accounts.

5.2. How it works

Cloudiway uses Exchange Web Services API (EWS) to migrate emails, contacts, and calendars. It is using PowerShell for mailbox permissions,shared, rooms and resources.

Note: all network operations are performed over TLS 1.2.

5.3. Source Prerequisites

5.3.1. Create source Exchange On Premises Service Account

You can migrate from Exchange On Premises in 3 different ways:

  • Impersonation: You need to create a migration account which must have impersonation rights, meaning it can impersonate all users.
  • Delegation: You need to create a migration account which has the right to access user mailboxes (you have Full access to each mailbox you want to migrate).
  • Self Service: Access to the mailbox with the username and password of each user.

To perform the migration, we recommend creating the Exchange On Premises account (service account) with impersonation privileges dedicated to the migration, that can be deleted once the migration is completed. This migration account is used to access the source mailboxes and needs to be provided in a Exchange On Premises Connector.

To enable the admin account to impersonate users, run this PowerShell command:

					New-ManagementRoleAssi​gnment -Role ApplicationImpersonation -User <admin_user_name>

More information about this PowerShell command can be found here.

5.3.2. Disable Throttling Parameters

Open the Exchange Management and type the following command and press Enter:

					New-ThrottlingPolicy CloudiwayPolicy
					Set-ThrottlingPolicy CloudiwayPolicy -RCAMaxConcurrency $null -RCAPercentTimeInAD $null -RCAPercentTimeInCAS $null -RCAPercentTimeInMailboxRPC $null -EWSMaxConcurrency $null -EWSPercentTimeInAD $null -EWSPercentTimeInCAS $null -EWSPercentTimeInMailboxRPC $null -EWSMaxSubscriptions $null -EWSFastSearchTimeoutInSeconds $null -EWSFindCountLimit $null -CPAMaxConcurrency $null -CPAPercentTimeInCAS $null -CPAPercentTimeInMailboxRPC $null -CPUStartPercent $null
					Set-Mailbox "Cloudiway" -ThrottlingPolicy CloudiwayPolicy

5.4.6. Create your shared mailboxes

Cloudiway provides a tool to provision and migrates shared mailboxes in a separate menu. In the Mail Migration section of the tools, you will see a Shared Mailboxes option. This tool can be used to discover your shared mailboxes and provision them to the target tenant so you don’t have to do it manually.

More details on how to use this feature can be found here:

5.5. Mapping Table

During the migration, Cloudiway uses a mapping table to perform the conversion of email addresses in email headers, calendar items, and mailbox permissions.

Important: the mapping table must be exhaustive, any missing email address will not be converted, and would end up with loss of mailbox permissions, unrepayable emails and broken calendar items. Cloudiway automatically populates this mapping table when source mailboxes are discovered by Get List functionality explained below. However, make sure if the mapping table was populated automatically that you are not missing any email address. 


6. Mailbox Migration

6.1. Create Your Connectors

For Cloudiway to migrate your Mailboxes, it needs to be able to communicate with both your source Exchange On Premises and target Microsoft 365 tenant. To do this, Cloudiway uses connectors. You will need to set up a connector for the Exchange On Premises you wish to migrate and target tenant that mail should be migrated to. Follow the steps from this page to configure your connectors.

Mail Migration Global Settings

Most of the options are self-explanatory.

The Convert Email Address option needs further explanation. The Convert Email Address option is switched on by default (and is best left on). When activated, this option rewrites email addresses found in the email headers, calendar items and mailbox permissions and replaces source email addresses with their corresponding target email addresses in the mapping table. Therefore, it’s important that all users exist in the mapping table before migration begins.

Archive Mails Older Than is to migrate the emails older than specified date and time in the past to the target archive mailbox and Migrate Everything to Archives is to migrate all the emails to the target archive mailbox. See the 7.3.2. Migration to archives section for further information.

Click on the Save button at the bottom of the screen to update your global settings.

6.3. Import or create your users into Cloudiway platform

There are a number of ways to add users that you wish to migrate. These include:

  1. CSV file import.
  2. Cloudiway’s mailbox discover tool (Get List).
  3. Create a single user.

Regardless, each user will need to be assigned a license type — Trial (limited to 100 MB), Education, Standard, Archive, or No License (used for adding users to your mapping table regardless of migration plans).

Note that importing users into Cloudiway won’t create the user mailboxes in the target tenant. See 5.6. Create your user mailboxes

6.3.1. Option 1: CSV file import

If you have a CSV file of all your users, you can upload the file to Cloudiway. The file must have the following fields in the header row:


Archive Mails

If required, click on Download sample CSV and add your users to the CSV file using the sample headers (FirstName; LastName; SourceEmail; TargetEmail; SourceRecipientType; TargetRecipientType; BatchName)

Upload Resource
Get List

The tool requires you to enter the Source and Target Pool of connectors.

Office365 Get Userlist

Then to specify:

  • The Matching Rule:
    • Mail Exact Match: the source email = the target email ( >
    • Keep Email Prefix Same as Source: only the domain name changed ( >
    • FirstName.LastName (i.e.
    • F.LastName (i.e.
    • FLastName (i.e.
    • LastNameF (i.e.
  • The Target Domain. Specify the target domain assigned to the target emails addresses in the list.

It will then add new users to the User List. You can monitor the progress of this task in the User List: Get List Logs.

User list

6.3.3. Option 3: Create a single user

Many of our first-time customers create a single user for testing purposes. This provides a means of watching the migration process without affecting all users.

Click on MANAGE > Create User and enter the following details:

Create new user

For more information regarding the different fields, check out this article. Repeat the process for any more users you’d like to create.

6.4. Activate and monitor your migration

Now that you have performed all the pre-migration steps within your tenants and within Cloudiway, you’re ready to migrate. We recommend you run a test migration on a single user first to check that your configuration produces the outcome you expect.

Cloudiway is an incremental migration platform that supports delta passes. Every time you restart the migration of a mailbox, only items that haven’t already been copied to the target will be migrated and for those already migrated items that have been modified in the source will be updated in the target. The platform, therefore, does not duplicate items in the target, just updates them.

The migration strategy usually consists of at least 2 migration passes, one before the cutover and another pass after the cutover:

  • 1st migration pass: which migrates the majority of the mailbox. Select mailboxes, click on MIGRATION, then the Start button. Explained below in more detail.
  • Cutover: You have to manually remove the domain from the source tenant, attach it to the target tenant and change the MX record in your DNS server. This is not automated by Cloudiway.
  • 2nd migration pass, delta pass: which migrates what hasn’t been migrated and updates modified items. Select mailboxes, click on MIGRATION, then the Start button. Explained below in more detail.
  • 3rd migration pass, delta pass: 24 hours after cutover you can submit an additional delta pass to make sure no residual email is left behind due to DNS propagation delays. Select mailboxes, click on MIGRATION, then the Start button. Explained below in more detail.

You can submit as many migration passes as you want for 3 months and until consuming the amount of GBs allowed by the assigned licenses but usually, you only need one before the cutover and another after the cutover. Find out more about the delta migration passes:

What a migration pass takes to complete depends on a lot of factors. Find out more about the migration performance:

If you have moved the source domain and need to perform one more delta pass, the Switch Domain global action will need to be used:

You can create user batches from the Batches tab to easily group subset of mailboxes. Click on the + icon and enter a batch name:


After creating the different batch, under Users tab, select the users you want to assign to a specific batch, click on BATCH button and Add to Batch:

User list

To start your migration, select the users or batch you wish to migrate.

  • For users, under Users tab, select all the users you want to submit and click on MIGRATION, then the Start button.
User list
  • For user batch, under Batches tab, select the user batch you want to submit and click on MIGRATION, then the Start button.

Your migrations will be scheduled and will begin as soon as cloud resources are available.

NOTE: When migrating by user batches during a long period of time you may want to enable email forwarders.

For more information, please see this article:

7. Other Migration Options

7.1. Mailbox permissions migration

You can migrate mailbox permissions for mailboxes through the Cloudiway platform.

Migration of permission isn’t performed during the migration of the mailboxes but through a dedicated job.

The migration of the permissions will migrate permissions on the mailboxes, on the primary and secondary calendars.

WarningIf permissions were applied to mail-enabled security group, the mail enable security group must exist at the destination for the permission to be applied correctly.

Click on User List, select the users, go to MIGRATION, then click on Migrate Permissions

Migration Permission

NOTE: Once you start the process of permissions migration, it cannot be stopped.

7.2. X500 addresses and LegacyExchangeDN migration

From the Transfer X500 section of Global Actions, you can migrate the X500 addresses and LegacyExchangeDN from your source mailboxes to your target mailboxes.

Select your Source and the Target, click on START.

Global Actions X500 Starts

You will see a Scheduled status, and Completed when the process is finished.

7.3. Shared mailbox migration

From the Shared Mailboxes section under Mail, you can recreate and migrate Shared mailboxes from your source tenant to your target tenant.

For more information, please see this article:

7.4. Rooms and Equipment mailbox migration

From the Rooms & Equipment section under Mail, you can recreate and migrate Rooms and Equipment mailboxes from your source tenant to your target tenant.

For more information, please see this article:

7.5. Distribution List migration

From the Distribution Lists section under Mail, you can recreate and migrate distribution lists from your source tenant to your target tenant.

For more information, please see this article:

7.6. Archive mailbox migration

7.6.1. Migration from archives mailboxes

To migrate your archives, create your users from the Archive menu.

Archive mailboxes

Once complete, select your entries, go to MIGRATION then Start.

Note: by default, archives are migrated to archives. You can eventually decide to migrate an archive to a standard mailbox.

Archive Entry Standards
Archive Mails

In this example emails older than April 7 2020 will be migrated to the archive mailbox:


Click on the Save button, when your migration starts, any emails older than the date you specified will be migrated to an In-Place archive. More recent items will be migrated to the target mailbox.

  • From the Global Settings section, Migrate Everything to Archives is to migrate all the emails to the target archive mailbox. In the Mail Global Settings, enable Migrate Everything to Archives and all emails will be migrated to the target archive mailbox:
Archive mails

Click on the Save button, when your migration starts, all emails will be migrated to an In-Place archive.

8. Troubleshooting

Cloudiway provides an extensive Help Center, also known as knowledge base, with many resources, including common error messages, guides, and downloads.