Is drive shipping best for large PST migrations to Microsoft 365?

Do you need to migrate thousands of PST files, really big mailboxes or large email archives to Microsoft 365 (and is drive shipping the answer?)

What is a PST file?

A PST file is an Outlook Data File (.pst) that can be used to store messages and other Outlook items.  From the ‘outside’ they look like a single file, but inside they have the structure of a pseudo mailbox.

Larger organisations in particular can have a legacy of many thousands of PST files sitting on individuals’ local drives, home drives and file servers.  They would historically get created as a way of staying within mailbox quota (when Exchange mailbox quotas on premises where perhaps not as generous as they are online).  PST files were also used as a convenient way of preserving mailbox contents – perhaps after an individual had left the company.   In fact PSTs used in these scenarios are widely considered a pest – especially when organisations switch to the cloud.

PST files can also be used as an interim store when migrating between platforms, as many mail systems can export emails and attachments into PST format, and conversely, import content from a PST file.  It is this ‘use-case’ that is the subject of this particular article…..

What is drive shipping?

Microsoft’s drive shipping service is multi-step process via which large amounts of data can be uploaded into Microsoft cloud via an interim device which is physically shipped to a Microsoft location.

This is how it works:

Instead of transferring data across the network, the technique involves writing PST files to a hard drive along with a mapping file (for example, migrate PST <filename> to <username> primary or archive mailbox).

The (encrypted) hard drive is then physically shipped to a designated Microsoft location from where data centre personnel pre-stage the contents into Azure.  The files are then ingested into Exchange Online according to the supplied mappings.

If you have TBs of emails you want to move into Microsoft 365, drive shipping via PSTs is an option open to you.

This Microsoft article goes into all the different iterations of what you need to do and the cost of using this service.

The same technique can be used to perform migration of mailboxes that are over 100GB in size or if the user’s mailbox contains one or more messages that exceed the 150-megabyte (MB) message limit (in which case resorting to PST files is recommended).

Using interim PSTs is also an option for migrating the contents from large email archives such as Enterprise Vault and EMC SourceOne, or email journals form platforms such as Mimecast.