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A Microsoft 365 email migration checklist

When an organization migrates its email servers and profiles to Microsoft 365, it could use several different processes. Sort through the five options listed below.

There are several different types of Microsoft 365 migrations, and organizations must choose one that aligns with their existing infrastructure. IT administrators should familiarize themselves with these five email migration methods to determine which process would be best for them.

1. IMAP migration

An Internet Message Access Protocol (IMAP) migration is a good option for organizations that use a third-party mail system such as Gmail or Yahoo Mail. The logistics of this type of migration can vary considerably based on the size of the organization and the number of users or employees.

At its simplest, this type of migration might involve dragging and dropping messages from one mailbox to another within Outlook. Another variation involves moving messages to a PST file and then migrating the file's contents to Microsoft 365. Organizations with larger mail deployments typically resort to using PowerShell to complete the migration process.

2. Cutover migration

The cutover migration method is helpful for small to medium-sized organizations with an on-premises Microsoft Exchange Server deployment consisting of fewer than 2,000 mailboxes.

However, it is worth noting that Microsoft only recommends cutover migrations for organizations with fewer than 150 mailboxes. Performance tends to suffer when administrators migrate more significant numbers of mailboxes. The main advantage of performing a cutover migration is that it is relatively simple -- all mailboxes, contacts and distribution groups migrate in a single operation.

The actual steps involved in the migration process vary depending on the type of migration and whether there are any third-party tools involved.

3. Staged migration

A staged migration is best for larger organizations that have too many mailboxes for a cutover migration. In a staged migration, IT admins migrate mailboxes in batches, and the migration process can take weeks or even months to complete depending on the size and number of mailboxes.

4. Hybrid migration

Hybrid migration is similar to a staged migration but with one key difference. A staged migration has the ultimate goal of migrating all of the mailboxes from the on-premises Exchange Server to the Microsoft 365 environment. The purpose behind a hybrid migration is to establish coexistence. Some mailboxes will migrate to Microsoft 365, while others remain on-premises indefinitely.

5. Third-party migration

Microsoft refers to this category as third-party migrations, but it just refers to various options from vendors that develop software and services to assist in the Microsoft 365 migration process. A third-party migration is any migration that uses one of these tools.

Executing the Microsoft 365 migration

The actual steps involved in the migration process vary depending on the type of migration and whether there are any third-party tools involved. Certain steps in the process will be common to all migrations, such as verifying the proper domain name with Microsoft and creating DNS records that will allow the Microsoft 365 ecosystem to work with the domain. Other steps, however, are largely dependent on the chosen migration path.

Microsoft 365 migration options
Choosing a type of Microsoft 365 migration

To provide a better idea of what is involved in the process, imagine that an organization wants to perform a simple cutover migration. Once the organization has completed the domain verification process, the organization's IT administrators would need to create a migration endpoint by connecting Microsoft 365 to its existing mail system. The option for creating a migration endpoint lives in the Exchange Admin Center under Recipients > Migration > More > Migration Endpoints.

The next step in the process is to create a cutover migration batch. This involves going to Recipients > Migration within the same console and then clicking on the New button and choosing to migrate to Exchange Online. Then, the IT administrators need to confirm that the correct migration endpoint is selected and initiate the migration batch.

When the migration process completes, there are a few cleanup tasks that IT will need to take care of. These tasks include:

  • Modify the MX DNS record to point to Exchange Online so mail will deliver to Microsoft 365 instead of to the on-premises environment
  • Delete the cutover migration batch
  • Assign Microsoft 365 licenses to users
  • Create an Autodiscover DNS record if it does not already exist
  • Decommission the old mail servers

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