Exchange 2003 Cutover Migration to the NEW Office 365 Blogs: A cut over migration is the simplest way to get all your existing email into Office 365. As the name implies, it’s a cutover from one service to another. Cutover migrations are supported for Exchange 2003, 2007 and 2010; for organizations with fewer than 1000 mailboxes. The setup and process is straight forward and nothing complicated. With any successful migration, some planning and testing of existing infrastructure is invaluable. Make sure that you plan and test the migration prior to trying to implement.



Before we can attempt the migration, we need to know what we are going. Microsoft has done a great job of providing good quality information for administrators to use, to plan the migration to Office 365. I always use the Exchange Deployment Assistant as a guide for all my migrations. This site is up to date and will cover most of all the migrations scenarios to Office 365


  2. Once the site is launched, you are presented three options. Since I am doing a simple cutover migration from Exchange Server 2003, I am going to use the Cloud Only option


  3. Click Cloud Only Blogs


  4. You are now asked a series of questions on end state goals and existing setup


  5. Answer all the questions


  6. Click the next arrow


  7. The Exchange Deployment Assistant will generate a step by step guide for you to follow. Make sure to read and understand what you are doing.




Using our guide from the Exchange Deployment Assistant, we need to make sure that our Exchange 2003 infrastructure supports RPC over HTTP and Outlook Anywhere. Use the guide to verify the Exchange 2003 setup. Once the setup is verified to be correct, use the Microsoft Remote Connectivity Analyzer to verify RPC over HTTP and Outlook Anywhere.


  2. Select the Outlook Anywhere (RPC over HTTP) test


  3. Click Next


  4. Enter all the information that is requested. Keep in mind that with Exchange 2003, using autodiscover to detect the settings will not work. Exchange 2003 doesn’t support autodiscover. These values will have to be entered manually


  5. Enter the Verification code


  6. Click Perform Test


  7. The test will start


  8. Once the test is successful, you can continue to the next step. If it’s successful with warnings, review the warnings and correct them if needed. I get a warning here, because I am using a multi-name UCC certificate. If the test fails, use the report generated and the guide (Exchange Deployment Assistant) to resolve the issues.





  2. Open Exchange Admin Center


  3. Click Migration


  4. Click the drop down menu and select Migrate to Exchange Online


  5. Select Cutover migration (supported by Exchange Server 2003 and later versions


  6. Click Next


  7. Enter on-premises account credentials


  8. Click Next


  9. Enter the on-premise Exchange Server


  10. Enter the RPC Proxy Server


  11. Click Next


  12. Enter a name for the New Migration Batch


  13. Click Next


  14. Select a user from Office 365 to get a report once the migration is completed. You can choose to automatically strat the batch or manually start the batch later.


  15. Click New


  16. The new migration batch is created and the status is set to syncing


This is where we wait for the migration to happen. Depending on the number of accounts and the ammount of data, this can take some time. You can view the migration details, by clicking View Details under the Maibox Status.

You will see the accounts provisionig on the Office 365 account and then start to sync from Exchange 2003 to Office 365.






When all the accounts are provisioned and the sync from Exchange 2003 to Office 365 is completed, you will get a report emailed to you. Once you get the report, you can complete the migration process.

  1. Migrate Public Folders – Microsoft has released a whitepaper for the companies that have public folders to migrate to Office 365. Migrate from Exchange Public Folders to Microsoft Office 365
  2. Assign Office 365 licenses to all the users. Use this BLOG post and jump to the section about assigning licenses – Creating Cloud Users for the NEW Office 365
  3. Verify that all the DNS records are updated and pointed towards Office 365 services. Use the DNS section in this BLOG post – Adding and Verifying a Domain for the NEW Office 365.  WARNING – Once you change the MX record to point at Office 365, there is some DNS replication time. During this time email will be delivered to either Exchange 2003 or Office 365. It’s important to keep your migration batch job running for up to 72 hours after switching the MX record.
  4. Configure the desktops to use Office 365 services – Use this BLOG post – Configuring Desktops for the NEW Office 365
  5. Once you are comfortable that all the email is migrated to Office 365 and the MX record DNS replication is completed, you can stop the migration batch job.


At this point the migration is complete and you can retire your Exchange 2003 services. Everyone should be happy cloud users.

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