The Evolution of Exchange Online Migrations – The Past and Today (Part 1)


For years, customers of any sizes have been busy migrating their on-premises messaging environment to Exchange in the cloud also known as Exchange Online. Since the BPOS days and up until today, there have been migration tools available directly from Microsoft or you could go with a third party product.

The migration story to Exchange Online was not exactly pretty back in the BPOS days, but over the years, it has been significantly improved, both when it comes to the options available, but also the quality of the tools used for migrating your mailboxes are much better nowadays.

In this article series, we will first take a walk down memory lane and talk about what was available up through the years. Then we will focus on the options available today. The Exchange Online migration tools team have spent a lot of resources on introducing new options over the years. Especially when it comes to the last year and we will dive more into these as we progress.

Let’s get going…

It Started with BPOS…

Back in September 2007, Microsoft laid out the next phase in its strategy for online services, offering a road map for new offerings that synthesize client, server and services software for people and businesses. They mentioned that these offerings would combine elements of client-based programs with software that runs large servers and new services delivered over the Internet. This was the Microsoft Online Services or in short MOS.

There were two key families of service offerings referred to as “Live” and “Online”. Live was what became Live@EDU, which as some of you may recall was an offering for education customers (schools and universities).

“Online” was for business customers and was later branded as Microsoft Business Productivity Online Standard (Microsoft BPOS) and was the very first version of we know as Office 365 today. It was a software as a service (SaaS) offering that consisted of Exchange Online (Exchange Server 2007), SharePoint Online (Microsoft Office SharePoint Server 2007), Office Live Meeting, and Office Communications Server (Office Communications Server 2007) much like we have with Office 365 today just with fewer workloads. Oh and then a very important difference was the fact that the 2007 line of products in BPOS were products that had been built for on-premises infrastructure purposes and not with cloud in mind.

Figure 1 below shows how the Microsoft Online Services Administration Portal looked like back then. Sorry for the poor quality of the image, it’s from my old Introduction to Exchange Online – Uncovering BPOS (Part 1) article series, and I couldn’t find the original screenshots I took back then.


Figure 1: Microsoft Online Services Administration Center (2009)

In order to migrate to Exchange Online in BPOS, you could replicate users from your on-premises Active Directory and migrate data from any Exchange 2000, 2003 or 2007 on-premises messaging infrastructure to Exchange Online using the Microsoft Online Services Migration Tools.


Figure 2: Microsoft Online Services Migration Tools Management Console


Figure 3: Migrating mailboxes to Exchange Online


Figure 4: Mailboxes in the process of being migrated to Exchange Online

If you wanted to migrate from a legacy (such as Exchange 5.5) or foreign messaging system such a Gmail, Yahoo, UW IMAP Server, Netscape, Sun One, Communicate Pro messaging environment to Exchange Online, we would use POP3/IMAPv4 based migrations.

Back then there were lots of organizations that used Lotus Notes and Microsoft developed its own tool to migration customer off Notes to Exchange. The tool was known as the Transporter Suite and provided not only an option to migrate from Notes to Exchange, but also included coexistence features. Bear in mind though, you could not migrate directly from Lotus Notes to Exchange Online. You had to first migrate from Lotus Notes to an on-premises Exchange environment using the Microsoft Transporter Suite and then migrate from there to Exchange Online. Alternatively, you could migrate from Lotus Notes using a POP3 or IMAPv4 based migration approach.

Figure 5: Microsoft Transporter Suite for Lotus Domino

As POP or IMAP based migration are far from ideal for an Enterprise organization, most Notes organizations used a third party migration product that could migrate directly from Lotus Notes to Exchange Online.

Prior to using the Microsoft Online Services Migration Tools to migrate the mailboxes, we would first synchronize the on-premises Active Directory user objects using a directory synchronization tool just like we do today for hybrid and staged migrations. Back then the tool was known as the Microsoft Online Services Directory Synchronization tool and was based on FIM/MIM just like the AAD Connect tool we have today. It was just much simpler as in, it could only synchronize objects to the BPOS tenant and nothing else. And yes lots of support cases was created around bug and issues with the sync tool back then.

Figure 6: Microsoft Online Services Directory Synchronization Configuration Wizard

After mailboxes had been migrated to Exchange Online, we would run the Delete Mailbox wizard to delete the on-premises mailboxes since this was done as part of the migration. Instead the user would have two sync mailboxes and mail would be delivered to the local mailbox and forwarded to the Exchange Online mailbox.

Figure 7: Deleting On-Premises Mailboxes

Much like is the case with hybrid deployments today, the Microsoft Online Services Migration Tool would convert the source mailbox user object to a mail user object (MEU) with a target address pointing to Exchange Online once the mailbox had been migrated.


Figure 8: Mail Contacts (user) objects in the Exchange Management Console


Figure 9: Target address set once the mailbox is migrated to Exchange Online

Since Exchange 2007 was the first version to use PowerShell, we could also use PowerShell or more specifically the Microsoft Online Migration Command Shell to migrate mailboxes to Exchange Online.


Figure 10: Using the Microsoft Online Migration Command Shell to migrate mailboxes to Exchange Online

This conclude 8 part 1 of this multi-part article series.

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