Migrating from third-party providers to Office 365 introduction

December 10, 2012 by Peter O'Dowd in IT Infrastructure, Technical Documentation


Having migrated a number of companies to Office 365, I think it would be valuable for me to share my experiences with the Office 365 community.

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 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 Migrate Mailboxes to Office 365 for Enterprises.

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 for developing your migration roadmap is to establish what features your email hosting providers provides. The following table shows a summary of the migration features possible with Office 365, 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, as 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 1 IMAP provider Example 2 IMAP provider
Domain name suffix tailspintoys.com Customer-specific; for example, contoso.com or treyresearch.com Customer-specific; for example, contoso.com or treyresearch.com
IMAP migration NO YES YES
Admin account with Full Access NO NO YES
Export org address book NO NO YES
Export Contacts NO YES YES
Export Calendar NO NO NO, but may be shared privately/publicly for access in Office 365

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 information relevant to small businesses, see the Office 365 Small Business home page.

For information relevant to medium-size enterprise businesses, see Office 365 plans for midsize businesses and enterprises.

A really useful plan advisor and cost estimator tool can be found at Microsoft Office 365 Advisor Tools.