Advanced Email Migration to Office 365 from a POP3 Service Provider – Part 2

 

Office 365 and DNS Setup for the Transition Email Domain

Because we are taking email for contoso.com (legacy) and need to have users in Office 365 receive email for that domain as well. We have to do some background forwarding that is transparent to the client and email sender. This is done with email forwarding from the legacy system to Office 365. In order to do this we need a transition (vanity) SMTP domain. For this example I will use mail.contoso.com.

  1. Primary Domain (contoso.com)
    1. Before we can migrate any users to Office 365, we need to have our domain setup and verified in Office 365. For this example I will use contoso.com. Since the email services are still at the legacy provider, do not switch the MX record. This domain will need to be designated as a Shared Exchange domain; this is very important. If this is not done, then the users that are migrated to Office 365 will not be able to send email back to the legacy email users.

     

  2. Configure the domain as a shared domain. To do this, follow these steps:
    1. Sign in to the Office 365 portal (https://portal.microsoftonline.com) as a global administrator or a service administrator.
    2. Click Admin, and then under Exchange Online, click Manage.
    3. In the Exchange Control Panel (ECP), click Mail Control, and then click Domains & Protection.
    4. Select the domain that is configured for mail coexistence, and then click Details.
    5. Select Shared, and then click Save.

     

  3. Transition Domain (mail.contoso.com)
    1. We will also need a transition domain (vanity domain) setup so that we can forward email from the legacy provider to Office 365. For this example I used mail.contoso.com. This domain will need to be setup in Office 365 for Exchange services only. Make sure that all the DNS records are added and verified so that this is a fully functional Office 365 email domain.

Now that we have the primary and transition domain setup correctly, this will now allow us to continue to the next steps.

Series of Posts

  1. Advanced Email Migration to Office 365 from a POP3 Service Provider – Part 1
  2. Office 365 and DNS Setup for the Transition Email Domain – Part 2
  3. Adding an Email Alias to an AD Account and Syncing Changes to Office 365 – Part 3
  4. POP3 Email Forwarding to Office 365 – Part 4
  5. Client Setup and Data Migration – Part 5

Thanks for visiting and reading my posts. I am always looking for more ideas. Please comment or email me with what you would like to see.

Kelsey Epps

Office 365 MVP

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10 thoughts on “Advanced Email Migration to Office 365 from a POP3 Service Provider – Part 2

  1. Tim Wilton

    I have a customer on Office 365 Small Business and I dont seem to have the option of creating a ‘shared’ domain to allow forwarding of mail to external recipients on the legacy domain. Is this because of the Office 365 Plan?

    Reply
      1. Tim Wilton

        I have added a second domain, however I dont have any option for adjusting Exchange settings, in particular ‘shared domains’. I think perhaps you can only do what you’re proposing using Office 365 Midsize Business plans or above, not on the Small Business Premium plans. Maybe someone can confirm this?

        Reply
        1. Kelsey EppsKelsey Epps Post author

          When using the P plan SKUs there is no access to the Exchange Management Console/Shell. How many users are you migrating? Send me an email with some more details and I can help you come up with a migration plan.

          Reply
  2. Beelzy

    Are these instructions still exactly valid for the current version of Office 365? For example, I don’t see Mail Control, and then Domains & Protection in the current version. If these instructions could be updated for the current version of Office 365 that would be really awesome.

    Reply
    1. Kelsey EppsKelsey Epps Post author

      This was written a few years ago and wave 14 of Office365. The theory is still the same, but the UI would be different.

      Reply

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