Migration from Exchange Server to Office 365

Summary: To ensure smooth migration from Exchange Server to Office 365, you need to do extensive and careful planning. There are many things to consider before you plan such an exercise. In this post, we’ve mentioned a complete checklist of the things you need to consider before migrating from Exchange Server to Office 365. This can help you in undertaking smooth and error-free migration process, with minimal downtime.

Most organizations and businesses opt for migrating from on-premise Exchange Server to Office 365 as the latter offers several benefits. Microsoft Office 365 has various benefits over Exchange server such as easy remote working, data security & control, flexibility & scalability and above all, no need for investing on the infrastructure. So, if you’re planning to migrate from on-premise setup to cloud, it is important to have a checklist to ensure smooth migration from Exchange server to Office 365. This checklist comes handy during the entire migration process – from planning stage to post migration.

The complete checklist is given below:

  1. Check your Existing Resources

The essential first step is to gather as much information about your prevailing Exchange environment. This helps in checking if your on-premise infrastructure meets the requirements for the Office 365 setup. You can take stock of the following:

  • Servers and components
  • Hardware and software
  • Network architecture and Domain Name System (DNS)
  • Authentication solutions
  • Bandwidth
  • Directory design
  • Certificates
  • Mail routing
  • Mail archiving and compliance
  • Mail and other client applications
  1. Identify Mailbox Size and Items

The next thing you need to do is assess the mailboxes size and the number of items in mailboxes that you want to move from Exchange to Office 365. As Office 365 is a cloud-based service, a clear idea about the mailbox size and items count can help you choose the best plan as per your needs.

  1. Identify the Content to be Moved
    Give proper consideration to the existing content such as folders, files and other business-related items that you’re planning to migrate from your existing setup to Office 365. If you’re planning to move Office templates, it is to be noted that upgrading the Office client may lead to changes in file format. As a result, you may face issues when you launch existing templates in the new setup.
  2. Clean up the Active Directory

You need to clean up your Active Directory on existing environment and update it, if required. This will help in synchronization, once your Office 365 is ready.

  1. Install Directory Synchronization Tool

You need to install and configure the Directory synchronization servers on your existing on-premises setup. When this process is complete, you need to activate the Directory synchronization in order to provision the user accounts.

  1. Check Bandwidth and Network

One of the important things is to conduct a bandwidth test on the internet connection of your company. This will help to calculate the migration process’ velocity and ensure that the connection will support the number of users you plan to migrate. You also need to open the ports required for communication with Exchange Online and configure URL filtering to put Office 365 websites on whitelist.

  1. Decide on the Office 365 License

Depending on the type of setup you want, there are various Office 365 licenses packages. Basically, there are three licensing options:

  • Basic: This option is suitable if you just want to migrate mailboxes and files. This subscription comes with 50 GB mailbox, 1 TB OneDrive and SharePoint.
  • Standard: If you want offline Office applications, you can to go with the Standard version.
  • Premium: If want to move full-scale into the cloud, go with the Premium as it features Offline Office Apps, Windows, and Enterprise Mobility Suite E3 (EMS).
  1. Choose the Migration Method

Choosing the right migration method is one of the most important things. This will define if the migration from Exchange server to Office 365 would be smooth or complex. There are various methods to migrate mailboxes from Exchange to Office 365. You need to choose the right method, depending on your existing version of Exchange server and the number of mailboxes you want to migrate. Some migration methods are:

  • Cutover Migration or Express Migration: This type of migration is suitable if you need to migrate less than 2000 mailboxes. This method supports Exchange 2003, 2007, 2010, and 2013.
  • Staged Migration: This migration method is ideal if you’re using Exchange 2003 or 2007, and need to migrate more than 2,000 mailboxes.
  • Hybrid Migration: This method is ideal if you want to maintain both on-premise email servers and cloud-based mailboxes. You can use hybrid migration if you’re running Exchange 2013 or Exchange 2010 with more than 150-2,000 mailboxes and need to migrate mailboxes in small batches.
  • IMAP Migration: You can use the Internet Message Access Protocol (IMAP) for migrating user emails from IMAP-enabled email clients such as Gmail, Yahoo, Outlook.com, Exchange, etc. By using this migration method, you’re able migrate just the inbox items and other mail folders.
  • Third-Party Migration Tool: Using a third party tool such as Stellar Converter for EDB is the easiest way to migrate mailboxes from Exchange server to Office 365. You just need to install the software, attach the mailbox database and with a few clicks export it directly to Office 365. It supports all the Exchange server versions – Exchange 2019, 2016, 2013, 2010 and others.
  1. Post-Migration Service Testing

Once you complete the migration process, you need to perform the testing to check the service functionality Office 365.

  1. Add Domain to Office 365

This is an important task post migration. You need to add domain to Office 365 and create DNS records for routing the domain traffic to the new cloud-based setup. You can add domain by using the Microsoft Online Services Customer Portal.

  1. Assign Licenses to the Migrated Mailboxes

You must assign licenses to the mailboxes migrated in Office 365 as they will be disabled after 30 days, without assignment of licenses. So, it is suggested that you assign licenses to mailboxes at the earliest.


There are many things that need to be considered, mentioned in the post, before you plan migration from Exchange server and Office 365. If you use native methods and techniques to migrate mailboxes from Exchange to Office 365, you should be prepared for downtime as the migration process may impact the availability of Exchange Server. On the other hand, you may face certain issues while using some manual migration methods such as possibility of data loss, error in synchronization, and others. For a safe, effortless and hassle-free migration of mailboxes from Exchange to Office 365, you can use a specialized EDB converter tool such as Stellar Converter for EDB. This easy-to-use tool directly exports both online and offline Exchange database (EDB) files to Office 365.

About Rajan Singh

Rajan Singh, a technical consultant. His expertise in MS products like SQL, Access, Excel, Outlook, Exchange, etc. Twitter Link -  https://twitter.com/rajansrinet

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