Microsoft 365 Mail Migration Guide

Overview

This Microsoft 365 Mail Migration UserGuide shows you how to migrate your mailboxes between Microsoft 365 tenants or to Google Workspace.

Cloudiway uses Exchange Web Services API (EWS) to migrate emails, contacts, and calendars. It uses PowerShell for mailbox permissions, shared mailboxes, rooms, and resources. All network operations are performed over TLS 1.2.

Prerequisites

To perform the Microsoft 365 Mail Migration, you need to configure an Entra ID Application with the appropriate permissions.

Entra ID Application

Cloudiway uses an Entra ID Application with Application Permissions to access Microsoft 365 mailboxes. This authentication method requires:

What is Migrated

The following items are migrated during a Microsoft 365 mail migration:

Limitations

The following items are NOT migrated:

• Email signatures
• Out of office messages
• Attachments to calendar events
• Public folders (not supported)
• Task steps and "add to my day"
• Conversation History (Skype history)
• External sharing links

Migration Process

The Microsoft 365 to Microsoft 365 mail migration is a five-step process:

Step 1: Create Connectors

For Cloudiway to migrate your mailboxes, it needs to be able to communicate with both your source and target Microsoft 365 tenants. To do this, Cloudiway uses connectors.

You will need to set up a connector for each source tenant you wish to migrate and each target tenant that mail should be migrated to.

Step 2: Configure Mail Settings

After setting up source and target connectors, open Mail > Mail Settings to define what is migrated and how.

Items to Migrate

Select the content types to copy: Emails, Trash / Deleted items, Calendars, Contacts, Tasks, Notes and Rules.

Convert Email Addresses

The Convert email addresses option is switched on by default (and is best left on). When activated, this option rewrites email addresses found in:

• Email headers
• Calendar items
• Mailbox permissions

It replaces source email addresses with their corresponding target email addresses in the mapping table.

Date Window

Set a From date and a To date to limit the migration to a period. Leave a date empty to migrate without that bound.

Archive Settings

The archive settings control which content is sent to the target archive and where it lands. They are described in Archive Migration below.

Step 3: Fill the User Mailboxes List

The User Mailboxes list (Mail > User Mailboxes) contains all mailboxes to be migrated. There are three ways to populate it:

Option 1: Discovery (Get List)

In Mail > User Mailboxes, click Get list to discover the mailboxes of the source Microsoft 365 tenant and pair them with the target.

The Get user mailboxes dialog opens. Specify the following parameters, then click Get list:

Option 2: Import CSV

In Mail > User Mailboxes, open the Manage menu and click Import CSV to upload a CSV file containing the mailboxes to migrate.

Option 3: Create User

In Mail > User Mailboxes, click Manage > Create user to add individual mailboxes manually. Enter the source email address and the target email address for each user.

Step 4: Verify the Mapping Table

Cloudiway automatically populates the mapping table when source mailboxes are discovered with Get list. Open Project Configuration > Mappings and make sure that every source email address is paired with the right target email address and that none is missing.

The Users tab lists each mapping with its first name, last name, source email and target email. Use the pencil icon to edit a row, New user to add one, or Export CSV and Import CSV to review and update the table in bulk.

It's important that all users exist in the mapping table before migration begins.

Step 5: Run Migration

Now that you have performed all the pre-migration steps within your tenants and within Cloudiway, you're ready to migrate.

For Individual Users

1. In Mail > User Mailboxes, stay on the User mailboxes tab
2. Tick the checkbox of each mailbox you want to migrate
3. Click Migrate in the toolbar

For User Batches

Batches let you migrate groups of mailboxes in waves.

1. In Mail > User Mailboxes, open the Batches tab
2. Click New batch to create a batch, then add its members
3. Click Migrate on the row of the batch you want to submit

Migrate Shared Mailboxes

Shared mailboxes have their own list. Discover them from Project Configuration > Discovery > Shared Mailboxes, then migrate them from Mail > Shared Mailboxes the same way as user mailboxes. The platform handles shared mailbox permissions automatically.

Migrate Rooms and Equipment

Discover room and equipment mailboxes from Project Configuration > Discovery > Rooms & Equipment, then migrate them from Mail > Rooms & Equipment. They are migrated with their calendar data and booking settings.

Delta Pass

Cloudiway is an incremental migration platform that supports delta passes. For more details, read our complete guide: Delta Pass Mail Migration.

Every time you restart the migration of a mailbox:

• Only items that haven't already been copied to the target will be migrated
• Items that have been modified in the source will be updated in the target
• The platform does not duplicate items, just updates them

Delta Pass Limitations

Cloudiway is a migration platform, not a synchronisation platform. For this reason, we limit the number of delta passes:

• You can submit as many migration passes as you want for 3 months
• Until consuming the amount of GBs allowed by the assigned licenses
• Usually, you only need one pass before the cutover and another after the cutover

Change Propagation

When migrating from Exchange or Microsoft 365, changes after migration are propagated including:

• Mail deletion
• Moving mail from one folder to another
• Mail marked as read
• Deletions from Google are propagated

When migrating from other sources, these changes are not propagated (the respective APIs do not propose a way to detect the changes between two passes).

X500 Aliases Migration

X500 aliases keep replies to messages sent before the migration working across tenants. In Mail > Mail Global Actions, click Run on Migrate X500: it transfers X500 addresses and the LegacyExchangeDN between the source and target tenants. Use Logs to follow the action.

Archive Migration

In-Place archives can be migrated separately or along with primary mailboxes. You can also migrate emails to the target archive based on age.

• Separately: open Mail > Mail Archives, click Get list to discover the archives of the source tenant, then migrate them like user mailboxes.
• By age: in Mail > Mail Settings > Archive settings, tick Migrate to archives and set Archive mails older than. Emails older than this date are sent to the target archive. Migrate everything to archives sends all content to the archive, and Archive location chooses between Online Archive and PST File.

Frequently Asked Questions