How to Create PST’s for Import into Mimecast

Cloud-based email continuity and archive services becoming more common in corporate email environments. Mimecast and Proofpoint are some of the more common cloud-based solutions for this. They provide an added layer of protection for mail flow and storage. Signing up and configuring the service is usually simple and straightforward. However, what if you want to move some of your messages from your current Exchange messaging environment over to the cloud service? Mimecast, for example, has a legacy data import service to do just that. Before you can import a PST, you need to be able to create one. Sometimes this can be an easy process, but most times this can get complicated quickly. I’ll walk you through how you can make this process a breeze in order to allow you to create PST’s for import into Mimecast successfully.

Reasons for Moving Content

When you first sign up for a service like Mimecast, it’s normal to set a start date for data ingestion. This would be the date on which Mimecast will begin to analyze and store your messages in its system based on your businesses needs. However, Mimecast allows you to send past content (referred to as legacy content) to their service. This gives you the following benefits:

  • Reduce the amount of data in Exchange
  • Add more protection to the content by ingesting it into Mimecast
  • Move Journal function from Exchange to Mimecast


Rules for Exporting Messages to PST

Knowing the rules for how to import PST into Mimecast will save you a lot of pain and frustration. Here’s a list of the common areas to focus on:

Date Range

Date ranges are helpful in reducing the amount of content that you plan to export out to PST. This saves you time by only exporting the content that Mimecast doesn’t have already ingested since starting the service. If you have any legal requirement to keep data for a certain amount of time, then using a date range is even more helpful. You can set lower and upper bounds for the date range. You would set the Upper Bound to be the date you started the Mimecast service and the Lower Bound can be the oldest date for a message. By doing this, all of the messages that you are legally required to retain would all reside within Mimecast and be protected.

Number and Size of Mailboxes

Knowing the number of Mailboxes involved is helpful, but the size is even more important. Large mailboxes will naturally create larger PST’s. The expectation is that the PST size for a single mailbox can be 1.5x the amount as indicated within Exchange. Also, the larger the PST, the more prone that PST will be for corruption. Here are some guidelines when it comes to creating your PST’s:

Whether or not to include Exchange Journal Data

Journaling within Microsoft Exchange can be very costly because a copy of each inbound and outbound message is saved to a Journal Mailbox. This mailbox can grow significantly in a short amount of time, so it requires constant monitoring. Mimecast receives all inbound and outbound mail, so it’s a natural fit to take on your businesses ongoing journal needs.

Including Journal mailboxes in your PST export process is the same as for end user mailboxes. The primary concern will be the size of the PST files as it’s a guarantee that they will be larger than 5 GB, so being able to define and split those mailboxes into multiple PST’s for the Mimecast import is important.

Per User (PU) or Not Per User (NPU)

Extracting content per user is preferred. This will allow your end users to find their email within Mimecast because ownership can be established during the Mimecast import process. Tools like the ExchangeSavvy Mailbox Connector can create the PST’s with the proper naming convention to help Mimecast determine ownership during the import process.

Message Classes

Cloud services such as Mimecast will not accept all message classes/types, so it’s recommended that you filter these out. Otherwise, you will be adding unnecessary time to your extraction time and the time it takes to import the PST into Mimecast.

If you have or had a third-party on-premise archive, then you might have shortcuts to archive messaging in your primary mailboxes. You will want to make sure that you apply a filter to ignore these shortcuts during the extraction process. Most third-party email archives are extracted to PST through a separate process, so ignoring them during the primary mailbox extraction is common.

Special Folder Exclusions

In some environments, there are special folders that are excluded from data retention policies. You will want to identify these early so that you can make sure you are exporting the expected content correctly. For example, you may have a folder called “important” that your legal team has determined can hold content beyond a set amount of time. If you are using the ExchangeSavvy Mailbox Connector for your extraction, you can easily list this folder to be excluded from the rest of the filters.


Exchange In-Place Archive Mailboxes

In Microsoft Exchange 2010 and later, In-Place Archive Mailboxes were introduced as an alternative to third-party archive solutions. If you are using Mimecast or Proofpoint as your email archive repository, then you will want to also consider exporting this content to PST. Archive mailboxes by there very nature are going to be larger than their primary mailbox, so being able to create PST’s of a defined size is critical.

Exchange Recoverable Items Folder

In some Exchange environments, user-deleted content will be stored temporarily in the Recoverable Items Folder. This is a hidden folder to the end-user and typically is in use if Litigation Hold (also known as Legal Hold) has been enacted. If Journal content is a concern, then it might be required to export content that is in this folder in order to meet internal/external compliance requirements.

If you plan on extracting contents from the Recoverable Items Folder, it’s advisable to create this as a separate PST from the primary mailbox extraction.

Reporting Requirements

Reporting is key to a successful extraction and will help guarantee accuracy when you import PST into Mimecast. A Chain of Custody style of reporting will help ensure accuracy by providing the following:

  • When an item was extracted
  • Source and Destination information
  • Whether or not it extracted or imported successfully

Handing over this information to Mimecast will allow them to cross-reference their import process. This will provide end-to-end confirmation for when you import PST into Mimecast.

Proceeding with your PST Extraction

The ExchangeSavvy Mailbox Connector can help fulfill all of the requirements of Mimecast for PST imports. Please click here to arrange a quick demo of how we can help guarantee a safe, quick, and accurate PST extraction!

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