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Why you definitely don’t need PST files in Exchange Online

9 Feb 2017 by Emma Robinson

We’ve previously looked in depth at the history of PST files and compelling reasons for eliminating them from your organization. But what are your options for dealing with the data they contain? And in particular, how can Office 365 help bring them back under your control?

PST files were designed to create additional storage in Exchange, enabling users to save files locally, reducing the load on the Exchange servers and network. This was a problem, when people had a 50MB limit on their mailboxes, but with an ever-increasing amount of low-cost storage available – Office 365 mailbox quotas jumped up to 100GB by default in December last year – it’s just simply not a problem any more, and there’s no reason to have them around.

Despite their faults, PST files can be very easy to ignore, existing in the peripheries of your environment, uncontrolled and often beyond the reach of established governance or data policies. But what happens when you decide to migrate? More and more organizations are opting for cloud-based email services like Exchange Online, just last week, Gartner released new research indicating that 8.5% of public companies are now using Office 365 for ‘cloud email’ and taking advantage of the tools available in this new environment.

More manageable, more versatile

Office 365 offers your end users a flexible, modern way of working, and it also comes with a whole new set of benefits and challenges when it comes to managing and optimizing your new environment. To fully embrace this new system, it’s important to consider any legacy solutions or systems you rely on – and the data that’s stored within them. This becomes increasingly important when you migrate to Office 365, as keeping them around can often incur additional costs which are unnecessary, as you now have access to alternatives in Office 365 which are typically included in your licence fee.

With its built-in compliance and eDiscovery features and secure, low-cost storage, Office 365 is an ideal target for PST data. Your data can be completely centralized, with no need to manage a third party system or to worry about interdependencies with other archives; everything can be managed in one place – the Exchange Online admin center.

Exchange Online admin center (courtesy Microsoft).

Choosing an Office 365 destination for your PST data

Archive mailboxes
If your PST files are not being actively used, and need to be archived, then you could migrate them to Exchange Online Archiving (EOA). This service is automatically included in Office 365 E3-E5 plans, and is available as an optional add-on to other plans using a per-user, per month subscription.

EOA creates what is known as an In-Place Archive, which can be accessed by a single user or entity (such as a shared mailbox), and there’s no need to wrestle with a separate interface to manage archived items. Your users are able to view messages in their archive mailbox, and can move or copy messages between their primary and archive mailboxes, in a similar way to how items were moved between OSTs and PSTs within a traditional Outlook client.

The difference between an In-Place Archive and a PST is that you now have central control of everyone’s archive. Data gets continually backed up and the system has built-in disaster recovery capabilities. It’s also readily searchable for eDiscovery, and can be placed on legal hold at the same time as the user’s primary mailbox.

Microsoft highlights that EOA is protected with physical and digital security measures that provide high levels of security and reliability.

  • Keeps important data in one place by giving users an In-Place Archive with a native, well-integrated user experience.
  • Immutably preserves and holds user information for discovery at later dates with Litigation Hold / In-Place Hold.
  • Delivers reliability, availability, and performance with a guaranteed 99.9% uptime, financially-backed, service level agreement.

Primary mailboxes
It is also possible to migrate data from PSTs into users’ primary mailboxes with Office 365. With 100GB mailbox limits available by default on plans E3 and above, storage presents little obstacle, and there are negligible practical differences between managing primary and archive mailboxes. They both offer the same security, resilience and retention features, for example.

Decisions about whether to provision primary or archive mailboxes as destinations for PST data could be affected by factors such as your compliance and regulatory requirements – or whether your Office 365 plan includes Exchange Online Archiving. There is the question of relevancy, with some suggestion that the whole concept of archive mailboxes has been made redundant by Office 365’s generous primary mailbox limits.

That said, it is important to note that archive mailboxes do not sync with local email clients. This is unlikely to present an issue as only recent email from the primary mailbox is normally synchronized with local OSTs and, as noted earlier, information can be readily copied between primary and archive mailboxes.

Considerations for migrating PSTs to Office 365

The Complete Guide to Eradicating PST Files outlines a five-step process for elimination:

  1. Prevent PSTs from being created or further data added to them.
  2. Locate PSTs throughout the environment.
  3. Establish ownership of PSTs.
  4. Ingest or import PSTs.
  5. Remove PSTs from users’ Outlook profiles.

In other words, the first thing you have to do is ‘lock down’ the PST environment, effectively turning all existing PSTs into non-modifiable archives. Your Outlook Group Policy template settings can be used for this.

PST settings in Group Policy Management Editor. In this Outlook 2013 administrative template under Miscellaneous/PST Settings the two relevant settings from the system registry (‘Prevent users from adding new content to existing PST files’ and ‘Prevent users from adding PSTs to Outlook profiles’) have been enabled. (courtesy: The Complete Guide to Eradicating PST Files).

Now that your PSTs have become fixed archives, you need to locate them and create centralized copies of them from wherever they’re stored (the original files should only be removed once full switchover to Office 365 has occurred).

These central copies then need processing and cleaning up. This is arguably more important when migrating over a WAN to Office 365 than to a local archive, as moving everything wholesale into Office 365 ‘as is’ is likely to mean migrating more data than you need to.

You should process corrupted files, duplicates and those without a clear owner to make your data is discoverable and compliant whatever target platform is decided – and you’ll need to strip out old passwords too. With Office 365 the smaller the WAN payload you can generate by doing this job thoroughly, the sooner the migration can be completed. Some form of intervention before your PST data gets within sight of Office 365 can make a real difference to timescale, efficiency, and level of success.

Dealing with leavers’ mailboxes

It’s likely that among the PSTs you discover will be plenty assigned to people who have since left the organization, so here’s a handy tip for Office 365 that can save you money.

For compliance it’s essential that the emails of these people – even if they moved on many years ago – remain accessible after migration. Unlike the archives of active users these items will never be modified, only searched.

Fortunately, if you manage your licensing carefully you need not incur unnecessary archiving costs in Office 365. To do this, you have to place the Leaver’s mailbox on Litigation Hold, and then remove the licence and Azure AD account. The Office 365 licence is freed up, and can be repurposed, but user’s data is still held within Office 365 and remains fully searchable, at no extra cost.

Make sure PSTs are in scope for your Office 365 migration project

When running a project to migrate email from on-premises Exchange to Office 365, many organizations realize belatedly that they’ve overlooked their PSTs.

Retrofitting a PST migration means a more rushed – and expensive – job, because data needs to be moved quickly to Office 365 to match the speed in which workstations are scheduled to be handed over to end users. It also provides limited time to train and assist those users in identifying and classifying their PSTs.

You may even encounter resistance from users who like being able to manage their own PST files locally, but even they can be won over with the promise that their email will work faster, more effectively, offer better mobility and that it won’t get corrupted any more in Office 365. As an Exchange admin you won’t keep getting distracted by PST recovery demands either, or end user performance issues (like this guy).

Exchange Online is only one potential target for PST files in Office 365. With the constant development being made to services like Office 365 Groups, and the arrival of brand-new applications like Microsoft Teams, there are plenty of new opportunities for liberating this shared, active PST file data. We’ll be taking a closer look at these options in the coming weeks – make sure you check back on the blog.