Migrating Exchange to Office 365 via Cutover Migration

In this article am I running through a cutover migration.  

Due to frankly enormous demand for migration services, my company has setup a dedicated team for Office365 migrations. You can view their website here:- www.migrateoffice365.co.uk If you are looking for help please get in touch!

The table below taken from Microsoft.com gives an overview of the different recommended migration paths.

Existing organization

Number of mailboxes to migrate

Do you want to maintain mailboxes in your on-premises organization?

Deployment option

Exchange 2010, Exchange 2007, or Exchange 2003

Less than 1,000 mailboxes



Exchange 2007 or Exchange 2003

No maximum


Staged or hybrid

Exchange 2010

More than 1,000 mailboxes



Exchange 2010

More than 1,000 mailboxes



Office 365 for professionals and small businesses

Fewer than 50 *

Not applicable **


Exchange 2000 Server or previous versions

No maximum



Non-Exchange on-premises messaging system

No maximum




Cutover – All mailboxes are moved into the cloud in one big hit. Best suited to smaller companies.

Staged – Mailboxes are moved in batches.

Hybrid – this enables you to move mailboxes over one by one. This requires the installation of an Exchange 2010 server. If you are not running exchange 2010 you can get an exchange 2010 hybrid license and you will need to setup a temporary exchange 2010 server.

Cutover Migration Plan Overview

  • Create migration plan
  • Add domain to office 365
  • Migrate Mailboxes
  • Change DNS records (aka redirect your email to Exchange online)
  • Create Distribution Groups and Contacts
  • Configure Clients
  • Decommission onsite Exchange server

Cutover Migration Pre-requisites\Considerations

  • Bear in mind any phones set to pick up emails via active sync (e.g. iphones, android etc) will need to be re-setup to connect to the office 365 mailbox. You will probably want to warn/pre-arrange with the end users.
  • Depending on the size of your mailbox store uploading all mailboxes can take quite some time. As you will not be able to use your current server in this time make sure you plan accordingly.
  • Microsoft enforce complex passwords for office 365 (although these can be disabled using powershell). You may want to pre-warn users about this.
  • You will need to have logon details for the Office 365 Portal
  • If you plan to run the full version of outlook on clients they must be using either Outlook 2007 SP3 or Outlook 2010
  • You will need to check for any 3rd party applications that plug into outlook or exchange. For example disclaimer software as this won’t work on Office365
  • You will need to have a valid public CA issued SSL certificate to migrate mailboxes unless you use the IMAP solution (which I don’t recommend as it only migrates emails). i.e. you need to have an SSL certificate for your OWA website.
  • If you want to use “single sign on” you will need a Win2008 or 2008r2 server to install AD FS 2.0.
  • I recommend changing the TTL on your MX record to 1 (hour). You will need to change DNS records in step 4 so make sure you are familiar with how to do this (usually via your ISP)
  • I also recommend asking all users to have an email clear out and to empty their deleted items – meaning there is less data to migrate.

Step 1 – Create Migration Plan

Logon to the portal (portal.microsoftonline.com) and create your migration plan.

Run through the plan and choose the appropriate options. Note that the options below are for a “cutover” migration from exchange 2003.

As mentioned in the pre-requisites when managing credentials:

  • Note that if you select “same set of credentials” aka “single sign on” you will need a Win2008 or 2008r2 server to install AD FS 2.0.
  • The directory sync tool cannot be installed on a domain controller.


Once you have finished you will get your own customised deployment plan as shown below.

Work through the list following the instructions at each stage. Certain sections as discussed further below.


Step 2 – Add your domain (to office 365)

This is where you add your internet domain (i.e. yourcompany.com) to office 365. In order to confirm ownership of the domain Microsoft ask you to create a specific DNS record as shown below


Step 3 – Migrate Mailboxes

I recommend disabling the SMTP server on your current email server to stop mail being delivered to your old server.

Fill in the below details. Note that the “exchange server” field is for the active directory FQDN, the “RPC proxy server” field is for the internet domain address.

Once this has completed you now have a copy of all of your mailboxes on Office365! Don’t forget to assign license to the new mailboxes.


Step 4 – Change DNS records (aka redirect your email to Exchange online)

You will need to change the MX record to ensure that your email is now delivered to Office365 and not your email server. You can find the office 365 MX record in the domain settings of the portal

Note the autodiscover record will help when creating Outlook profiles for remote users.


Step 5 – Verify/Create Distribution Groups and Contacts

I recommend manually checking that all distribution lists and contacts have come across. Again this is done in the portal.


Step 6 – Setup Clients

  • Assuming the autodiscover DNS record has been created then setting up the new Outlook profiles should be a doddle. If for whatever reason you need to manually setup Outlook, please see my other article for instructions on setting up Outlook.
  • Start outlook with the /importnk2 switch to automatically import the old nk2 file to the new profile. See this article for further info.

You can also install Office 365 Desktop Setup (optional)

  • Sign in to the Office 365 portal by using the same credentials that you used to log on to Outlook.
  • In the Office 365 portal, in the right pane under Resources, click Downloads.
  • Under Set up and configure your Office desktop apps, click Set up.


Step 7 – Decommission onsite Exchange Server

After everyone is migrated it is recommend to uninstall the old exchange server.



Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.