What Are Microsoft Outlook's File Types for eDiscovery?

20 September 2021 by Ross eDiscovery

Takeaway: Outlook stores your emails primarily as MSGs, EMLs, PSTs, OLMs, and OSTs. But ideally, you don’t want to use Outlook for eDiscovery because it hangs regularly, changes email metadata, and has compatibility issues. Instead, find an affordable Cloud eDiscovery service that can handle all Outlook’s file types.

Outlook was revolutionary because it lets us work on emails even when not connected to the internet. But it gives us other tools, too – like an address book, calendar, to-do list, and more. So, rather than just being an email client, it’s more of a personal information manager.

But how do we use Outlook’s data for eDiscovery? First, we need to explore its file types.

You’ll come across the following files when collecting Outlook data for eDiscovery. (Note: There are other rarer file types but they don’t pop up often, so we can skip them for now.)

1. MSG & EML files: How Outlook stores single emails.

  • An MSG file (with a ‘.msg’ file extension) is how Outlook exports single emails from your mailbox to your PC. So, when you drag-and-drop an email from Outlook into Windows, it gets converted into an MSG file. These are easy to share and have the email’s entire contents – including links, attachments, and details about who sent it, when it was sent, etc.
  • An EML file is how Outlook exports single emails from your mailbox to your Mac. It’s the Mac equivalent of an MSG file, but it’s a format that Apple Mail also uses. (You’d create an EML using Apple Mail by going to ‘Save As’ > ‘Format’ > ‘Raw Message Source’.) The great thing about EMLs is that you can open them using a simple text editor like TextEdit.

2. PST and OLM files: How Outlook stores groups of emails.

  • PSTs: When you export an individual email, it’s stored as an MSG. But when you export an entire mailbox, it’s stored as PST (i.e., Personal Storage Table), instead. PSTs are a convenient way to archive old emails or group them into batches. For example, with eDiscovery, each custodian’s mailbox will be stored as a separate PST.
  • An OLM (Outlook for Mac) file is the Mac-compatible version of PSTs. I.e., it’s the file type created when you export an Outlook mailbox onto a Mac. (Note: PSTs and OLMs usually contain emails, but more broadly, they’re archive files. So, they can also include calendar entries, contacts from your address book, tasks on your to-do list, notes, and more.)

3. EDB files: How your emails are stored on Microsoft’s servers.

Outlook lets you tackle your email offline and then syncs it when you’re back online. But what is it syncing with? That would be the Exchange Server – Microsoft’s advanced computer server that stores all Outlook users’ emails, tasks, calendars, etc. And it stores your PSTs/OLMs as EDB (Exchange Database) files.

4. OST files: How your emails are stored when you’re offline.

When you’re online, Outlook syncs your emails with the Exchange Server. But what about when you’re offline? Here, Outlook temporarily stores your data as an Offline Storage Table (OST) and syncs it with a corresponding PST when you’re back online. OSTs are tricky, though, because if they don’t sync with a PST correctly, you could lose vital emails.

The problem with Outlook is that it’s not ideal for eDiscovery.

Outlook was revolutionary when it first came out, but it’s quickly been overtaken by competing email applications like Gmail. More importantly, though, it gets in the way of good eDiscovery.

1. Outlook isn’t reliable. It often hangs, crashes, and loses your data.

Outlook gets heavily criticized because it hangs so often. For example, you’ll often see it get stuck when loading – especially when you’ve archived a lot of emails in a large mailbox. And the add-ins developed to help it run smoother often end up crashing it instead. Also, Outlook will lose your emails if you try and sync them from different computers. But the biggest problem is that PST files get corrupted easily, especially as they grow in size. These are all dealbreakers for eDiscovery, where you can’t afford to lose your client’s data.

2. Using Outlook to open emails changes their metadata.

When you create an email, it gets stamped with a bunch of information. Things like when it was created, who created it, when it was sent, who received it, and so on. This type of information – called metadata – is a digital footprint that tracks the history of an email. The issue is that accessing an email through Outlook will change parts of its metadata, and so is similar to (unintentionally) tampering with evidence. This makes Outlook a poor choice for email eDiscovery.

3. Outlook isolates Mac and PC users.

Although you can use Outlook on both PCs and Macs, it’s tough to transfer files between them. For example, you can’t open PSTs and MSGs on a Mac and can’t open OLMs in Windows. This might be solved with the rumored ‘universal Outlook client’ that Microsoft is building, but for now, these compatibility issues are a problem for eDiscovery.

The solution? Use specialized eDiscovery software for email eDiscovery, instead of Outlook.

Cloud eDiscovery applications are by far the best way to handle email eDiscovery. Here, you subscribe to an eDiscovery service that runs in the Cloud (a global network of high-powered computer servers) and is managed by your eDiscovery provider. So, instead of trying to operate the software yourself, you simply log in via your web browser and log off when you’re done. More importantly, though, you can upload MSGs, ELMs, PSTs, OLMs, and more without changing their metadata. Plus, you’ll have access to a range of valuable eDiscovery tools to make advanced searches, tag related documents, [readact sensitive information]](https://goldfynch.com/blog/2020/09/17/the-right-way-to-redact-ediscovery-productions-and-why-drawing-little-black-boxes-isnt-enough.html), and produce your files.

Using dedicated eDiscovery software brings other perks, too.

A Cloud eDiscovery application like GoldFynch can help you cut costs even as it gives you the tools to handle email eDiscovery.

  • It costs just $27 a month for a 3 GB case: That’s significantly less than most comparable software. With GoldFynch, you know what you’re paying for exactly – its pricing is simple and readily available on the website.
  • It’s easy to budget for. GoldFynch charges only for storage (processing is free). So, choose from a range of plans (3 GB to 150+ GB) and know up-front how much you’ll be paying. You can upload and cull as much data as you want, as long as you stay below your storage limit. And even if you do cross the limit, you can upgrade your plan with just a few clicks. Also, billing is prorated – so you’ll pay only for the time you spend on any given plan. With legacy software, pricing is much less predictable.
  • It takes just minutes to get going. GoldFynch runs in the Cloud, so you use it through your web browser (Google Chrome recommended). No installation. No sales calls or emails. Plus, you get a free trial case (0.5 GB of data and a processing cap of 1 GB), without adding a credit card.
  • It’s simple to use. Many eDiscovery applications take hours to master. GoldFynch takes minutes. It handles a lot of complex processing in the background, but what you see is minimal and intuitive. Just drag-and-drop your files into GoldFynch, and you’re good to go. Plus, you get prompt and reliable tech support.
  • Access it from anywhere, and 24/7. All your files are backed up and secure in the Cloud.

Want to find out more about GoldFynch?