Email Migrations to the Cloud and Enterprise Archives


In our ever-evolving world of cloud-based architecture, it is not uncommon for an organization to contemplate moving their electronic mail system to a hosted architecture.  The business benefits to this are well published and there is no need to bring them up today.  Obviously the largest of the hosted email systems is Microsoft’s Office 365.  The underlying architecture behind this technology was developed specifically for hosting multiple organizational email systems via a common platform while still maintaining a high level of independence and security for each organization on the platform.  This is the basis of Microsoft’s Multi-Tenant infrastructure.

Moving messaging systems to Microsoft’s Office 365 (O365) has been a viable option for organizations for well over a decade.  Thousands of organizations have made the move already, and thousands more are poised to do so.  Typically, when a company decides to migrate to O365 it is a priority to move the legacy production email first and foremost.  This could be a Lotus Domino infrastructure or a Microsoft Exchange infrastructure.  In either case you must create destination accounts in Office 365 for your email.

In the case of a Lotus Domino environment, the organization will also need to address coexistence.  Regardless of which vendor they use for this, Microsoft Azure Active Directory Synchronization will be an integral part of the coexistence solution.  Similarly, if the organization is moving from Exchange to Office 365 they can use the same Microsoft Azure Active Directory Synchronization to move mailboxes to Office 365.

In enterprise scale companies, there is often a legacy archive solution in place.  This archive may contain data going back 15 years or more.  Organizations that employ enterprise archiving solutions, do so for compliance, regulatory, and/or legal reasons.  It would make sense that, should there be a need to store that data, these same organizations would contemplate moving that legacy data as well.

One question that always comes up during data migration discussions is: What data should we move first?  Should we move current users first to eradicate the on premises email solution or should we move the archives first?  The answer to this depends on the requirement surrounding the data in the enterprise archive.

These enterprise archives will contain data for users who have left the company over time.  It is not uncommon for the number of departed users, and their associated data, to be significantly higher than that of current employees.  Consider that each user mailbox moved to Office 365 requires a valid user mailbox, this could mean that a significant number of additional Office 365 licenses will be required to move the enterprise archive users to Microsoft Office 365.  This can come as quite a surprise for companies.

By employing the Azure Active Directory Synchronization to create mail-enabled users in Microsoft Office 365, administrators can create an online archive in Microsoft Office 365 that is linked to each user’s on-premises Exchange mailbox.  This would allow the archived data to be migrated to the Online Archive in Microsoft Office 365 even though the user is still accessing his or her Microsoft Exchange Mailbox on premises.

Now think back to my earlier statement that each user mailbox moved to Microsoft Office 365 must have an active mailbox to migrate data.  If a company were to move 2,500 users to Microsoft Office 365 they would typically acquire the number of licenses to correspond to the number of active users.  If they move all 2,500 users’ live mail to Microsoft Office 365 and they have only purchased 2,500 Microsoft Office 365 licenses they cannot migrate the data in the Archive until they purchase additional licenses.  Imagine the cost if the number of user mail archives were in the range of 10,000 users.  The licensing fees would make this very expensive.

One of the features that Microsoft has enacted with Office 365 licensing is that when a user leaves the company, the Microsoft Office 365 admins can identify this individual as a “leaver” which will allow them to keep the mail in Microsoft Office 365 and remove the Office 365 license for the user.  This does not delete the license but rather frees it up for re-use.  Keeping this thought in mind, how might an organization leverage this to migrate enterprise archives?

If during the analysis aspect of an archive investigation, the list of departed users is identified, accounts in Microsoft Office 365 can be created to migrate the departed user data into.  These users can then be classified as a leaver, the mail will be retained in Microsoft Office 365 and the user is removed from Microsoft Office 365 and the license is now available for another user to be created.

This allows for the migration of departed user data first, which will minimize the number of licenses required to migrate the total user base.  It is recommended that these departed users be done in groups rather than as a whole.  If we consider the 2,500-user license purchase, perhaps these departed users are migrated in groups of 500.  This could allow the other 2,000 licenses to be applied to live users.  The other 500 are reallocated to other departed users to exercise the migration of that data by reusing the same licenses repeatedly.  As live users are migrated from an email perspective, their associated archive data can also be migrated to Microsoft Office 365.

This method will help minimize the Office 365 licensing costs associated with the departed users and allow for the retirement of both the on-premises email system as well as the legacy archive solution.