Office 365 PST Import Overview

February 17, 2017 Chris Johnson

Do enough Office 365 mailbox migrations for customers, and you will notice many wrinkles in the process. On the surface, it may seem straight forward when it comes to deciding to move your organization to Microsoft’s excellent service, but it also can cause major frustrations that could lead to a failed migration, or a very bumpy ride for your users. One item that is appearing more and more is how to deal with the importing of very large mailboxes or archives into Office 365. 

While it would be nice to use the mailbox migration GUI to simply get an entire user’s mailbox into Office 365, there are scenarios in which this may not be the only tool you use to get all mail up to the cloud. The source mailbox could be in the hundreds of gigs. Or what if your organization has been using a third-party archiving service, but now it’s time to recall the PST files for your organization, and you’re tasked with finding a way to import all mail into every user’s Exchange online archive? 

Microsoft provides a few built-in solutions for uploading PST files en masse into Office 365. One way is to simply place all of the PST files on a hard drive and ship it to Microsoft. This is a great option if you’re moving a mass amount of PST files, and/or you are getting poor upload speeds to Azure, the location the PST files are held while importing into their respective mailboxes. 

Uploading PST files yourself into the Azure storage is an option as well. Using Microsoft’s Azure AZCopy command line utility, uploading mass amounts of PST files is very possible. Due to throttling, this process can take days, or even weeks to complete depending on the amount of mail to import. Once the mail is inside of the Azure storage, PST import jobs are now able to be created for ingesting into mailboxes. 

Some tips from the field if using the PST import is a decided strategy for your Office 365 implementation… 

  • PST uploading into the Azure storage and mailbox migrations can take place at the same time.
  • You’ll want to make sure retention policies and any other compliance policies that are in place is disabled temporarily while importing mail.
  • Create a dedicated machine for importing PST files, as the uploading can take an extremely long time
  • Consider provisioning your own Azure storage, uploading the PST files there, and then do the imports. Using the advertised Import Service drives you down a sluggish GUI experience when it’s time to import. Going at it on your own allows you to use Powershell, and bypass the sometimes slow GUI.

As a part of the Microsoft Consulting team at Arrow Systems Integration, we're staffed with engineers that not only are passionate about the cloud, but they also possess years of experience in the education, architecting, and deployment of Office 365 solutions for small, mid-size, and enterprise organizations. Please reach out, and we can talk about a custom Office 365 migration plan.

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About the Author

Chris Johnson

Microsoft Solutions Consultant

Chris Johnson is a Microsoft Solutions Consultant at Arrow Systems Integration with specific focuses in Windows Server Infrastructure, Exchange, Active Directory, Direct Access, Office 365 and much more. Chris has nearly 20 years of IT experience working with customers on a variety of initiatives surrounding the Microsoft stack. He has worked in several environments from small to midsize businesses up to large, global enterprises. While experienced in many areas, recently his roles have included systems administration, development, and consulting with a focus on Microsoft and Linux.

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