infoTECH Feature

May 07, 2020

Migrating Mailboxes from Exchange to Office 365: What You Need to Know

Email plays an important role in communication of any organization. It remains the backbone of all business communications.

Most organizations and businesses use on-premise Exchange server for email communications. This means the organization takes full control over the physical hardware of Exchange server. Thus, it becomes a responsibility of the organization to maintain, upgrade, and secure the Exchange server regularly, which often requires additional resources, cost, and human-hours.

With the introduction of Office 365, Exchange services can be moved on the Cloud which makes it easier to manage and eliminate the hassle associated with server maintenance, security, and management. Also, Office 365 offers better security, functionality, stability and scalability features with minimal to no downtime.

All these features and other benefits make Office 365 an ideal solution to the problems and challenges that an organization faces with on-premise Exchange.

However, moving mailboxes from on-premise Exchange server to Office 365 is a complex process. It requires extensive planning and choosing the right method for an error-free migration.

Here are two key points to remember for smooth migration of on-premise Exchange mailboxes to Office 365.

1. Migration Planning

Performing mailbox migration requires careful planning to minimize the downtime and avoid any errors. Also, backup solutions for just in case scenarios when something goes wrong. It requires careful consideration of every aspect and technical requirements before heading for migration.

Also, consider factors such as training required by IT staff to understand various migration methods and how to use them for seamless migration.

Cost is another factor that may strongly influence your decision. Migration may take a few days to complete based on the method you choose to migrate mailboxes from on-premise Exchange to Office 365. Estimate the cost of human hours and resources that might be required to carry out the migration.

Also, risks associated with some migration methods, such as directory synchronization error and other problems that may appear during migration.

2. Migration Method

Choosing the right migration method is critical. There are a few methods that you can follow to migrate mailboxes from an Exchange server to Office 365,

  • Cutover Migration
  • Internet Message Access Protocol (IMAP) Migration
  • Staged Migration
  • Hybrid Deployment
  • Third-Party Migration Tool

Each method has its own benefits and limitations when it comes to migration-premises Exchange mailboxes to Office 365.

  • Cutover Migration

Also known as Express Migration, Cutover Migration lets you migrate all mailboxes from your on-premise Exchange 2003, 2007, 2010, or 2013 to Office 365. If you want to migrate whole Exchange environment to Office 365 at once, choose this method.

You can perform Cutover Migration from the Exchange Admin Center (EAC) and move up to 2000 mailboxes. However, it’s recommended to migrate no more than 150 mailboxes at once as it can take a lot of time to create and migrate a batch of 2000 mailboxes by using Cutover Migration.

  • IMAP Migration

This migration method is used for moving the IMAP email accounts such as Gmail, Exchange, or other IMAP accounts. It can migrate up to 500,000 mailbox items from user mailbox. However, IMAP migration only allows you to migrate items in inbox and other email folders. It does not migrate other mailbox items such as contacts, calendar, tasks, notes, etc.

Also, this method doesn’t create a mailbox in Office 365. You need to create a mailbox for each user before migrating the mailboxes.

  • Staged Migration

Staged Migration is suitable for those who want to establish a permanent mail coexistence with their on-premises and online Exchange, i.e. Office 365. Staged Migration is performed over time, in stages.

It’s suitable if you want to migrate more than 2000 mailboxes from your current Exchange environment to Office 365. In this method, admin is required to synchronize accounts between office 365 and on-premises Exchange server Active Directory (AD).

This allows you to migrate only the user and resource mailboxes. Further, each user is required to create a new Outlook profile in Office 365.

Unfortunately, this method works only for Exchange 2003 and 2007.So, if you need to migrate mailboxes from Exchange 2010 or later version to Office 365, use Cutover Migration or Hybrid Deployment method.

  • Hybrid Deployment

Hybrid Deployment is a modern Staged Migration method that can be implemented in Exchange 2010 and later versions. It offers the ability to extend a feature-rich experience and admin control that you currently have on your on-premise Exchange environment to Cloud-based Office 365. It integrates the look and feel of both Office 365 and on-premise Exchange after migration into a single Exchange.

Although Hybrid Exchange Deployment is complex to implement, it provides an overall best user experience when compared to other migration methods. Both on-premise and Office 365 function seamlessly and appear to be the same environment. This also allows admins to offload mailboxes from Office 365 to on-premise Exchange without additional resources or third-party tools.

Like Staged Migration, Hybrid configuration requires directory synchronization. But if for some reason directory synchronization can’t be implemented, there’s no other choice but to use a third-party migration tool.

  • Third-Party Exchange Migration Tool

A third-party Exchange to Office 365 migration tool such as Stellar Converter for EDB makes the whole process of migrating mailboxes from Exchange on-premises to Office 365 much easier and more convenient.

This GUI-based Exchange migration tool is easy-to-use and doesn’t require any training or deep understanding. All you need to do is create an offline copy of Exchange databases, scan the databases with this tool and then export the mailboxes directly to Office 365.

The software lists Source (News - Alert), Destination and Map Mailboxes options which let you map and migrate mailboxes to Office 365 users. This is the most recommended EDB to PST Converter tool by MVPs.


Now that you know the key points to consider for migration of mailboxes from on-premise Exchange to Office 365, do not start the migration process just by learning the benefits and disadvantages. Thoroughly read all the migration methods and process of migration before implementing.

If possible, create a test environment and see if the migration process works. This will give you hands-on experience and help you migrate your on-premise Exchange mailboxes safely to Office 365.

And if you want don’t want to go through all the hassle, it’s better to implement a third-party migration tool such as Stellar Converter for EDB.


Subscribe to InfoTECH Spotlight eNews

InfoTECH Spotlight eNews delivers the latest news impacting technology in the IT industry each week. Sign up to receive FREE breaking news today!
FREE eNewsletter

infoTECH Whitepapers