Migrating to Exchange Online Introduction

March 18, 2013 by Dennis Rea in IT Infrastructure, Office365, Technical Documentation


Microsoft recently released the next generation of Microsoft® Office 365. This exciting new release includes Microsoft Exchange Server 2013, along with the latest versions of the other Office 365 suite of applications.

In this article, I’ll describe how to migrate from third-party email hosting providers to Office 365 Small Business Premium or Office 365 Small Business.

Having migrated a number of companies to the previous version of Office 365, I’m keen to share with the Office 365 community my experiences in migrating to this new generation of Office 365.

Every migration I’ve done has met with the customer’s satisfaction; however, the effort required in getting to that point varied considerably, and I’ve learned valuable lessons along the way. Hopefully, by reading this article you will be able to put together a roadmap for migrating your company, or a customer, to Office 365 Small Business and also save yourself time. This article is written for those involved in migrating a small to medium-size business to Office 365 from a hosted provider. Although the article is technical in nature, providing step-by-step instructions, a nontechnical audience will also gain valuable insights regarding the high-level steps required for migrating their company.

In this article, I am only going to deal with migrating from third-party email hosting providers. Migrations from an on-premises Microsoft Exchange deployment to Office 365 are covered in depth in Mailbox Migration to Exchange Online.

About the Author

Peter O’Dowd is a longtime Exchange MVP, consultant, trainer, and author. He has worked closely with Wadeware for 10 years developing technical content for Microsoft Exchange.


Email hosting providers come in many forms and varieties

The first step in developing your migration roadmap is to establish what features your email hosting provider provides. The following table shows a summary of the migration features possible with Office 365 Small Business, with examples of third-party email hosting providers. The steps required to perform these migration features are fully described, along with screenshots, throughout this blog.

Those of us who are familiar with Office 365 functionality are used to features such as:

  • Exportable Global Address Lists (GALs)
  • Multi-level folders in mailboxes
  • Attachments, read/unread status
  • Calendars, meeting rooms, shared mailboxes
  • Shared contacts
  • Administrator-assigned permissions
  • User-delegated permissions

We take these features for granted because Office 365 with Exchange Online provides them. However, the world of POP and IMAP providers is very different, and many of these features/capabilities are not provided. Unfortunately, the absence of some of these features – e.g., exportable GALs or administrator-assigned permissions – can add extra effort to the migration.

The following table describes three common provider types and their capabilities.

Capability Example POP provider Example IMAP provider Example Hosted Exchange provider
Domain name suffix Tailspintoys.com Customer-specific; for example, contoso.com or treyresearch.com Customer-specific; for example, contoso.com or treyresearch.com
Cutover migration NO NO YES
IMAP migration NO YES YES, but cutover migration is preferable
Admin account with Full Access NO YES YES
Export Contacts NO YES YES
Export Calendar NO NO, but may be shared privately/publicly for access in Office 365 YES, the calendar is migrated along with the other mailbox contents


Most migrations involve the following list of common tasks:

  • Register and subscribe to Office 365.
  • Verify your domain name to Office 365, to configure it as an accepted domain.
  • Create users/mailboxes.
  • Migrate the mailbox data, Calendar, and Contacts where possible.
  • Maintain a period of coexistence between the old and new environments.
  • Point the mail exchanger (MX) record to Office 365.
  • Decommission the email provider’s mailboxes.

To get the most from this blog, look at the preceding table and decide which of the three examples most closely resembles your provider. Then click the link to the section in this article that describes the migration steps required to create your roadmap:

For information on registering/subscribing to Office365, as well as other relevant information see Select an Office 365 business plan.