Challenges faced by Organizations while Migrating PST Files to Office 365

Unlike on-premises Exchange Server or Microsoft Outlook, one cannot simply select and import a PST file into Office 365 tenant via import wizard. Instead, the administrator has to follow a specific process or set of instructions to create mailboxes, assign licenses, upload PST files, map mailboxes, and create an import job before they can start importing or migrating them to Office 365 mailboxes. The process is long and complex due to the security and compliance requirements in Office 365.

In this article, we have discussed various challenges that you may encounter while uploading and migrating PST files to Office 365.

But before we discuss the challenges, you must know the two manual methods or import job types used for uploading, importing, and migrating PST files to Office 365 .

1. Network Upload

In this method, you create a new import job in Microsoft 365 or Office 365 under Security & Compliance section and copy the SAS URL. Then use the Azure AzCopy — a command line-based tool — to upload PST files to Azure Storage via SAS URL. You must also create a PST import mapping file and upload it to Microsoft 365. The file is used to import the PST files into user mailboxes on Office 365.

2. Drive Shipping

In this method, you copy the PST files in a BitLocker-encrypted hard drive and ship the drive to one of the Microsoft centers. After receiving the drive containing PST files, Microsoft processes and uploads the files to a temporary Azure Storage location.

Once the PST files are uploaded, you can start the Microsoft 365 or Office 365 PST import service to migrate the mail items from PST files to Office 365 mailboxes.??

Below is a diagrammatic representation of PST import workflow in Office 365 via Network Upload and Drive Shipping methods.

Challenges While Migrating PST to Office 365

You may encounter various challenges while migrating PST files to Office 365. Below are some common challenges associated with migrating PST files to Office 365.

1. Export PST Files

Outlook only creates PST files when you add a POP (POP3) email account. For IMAP, Exchange, and Outlook.com accounts, Outlook creates an Offline Storage Table or OST file. Thus, you must ask users to export their mail items using the Outlook Import Export wizard and share the PST file, which you collect and store at one location on any Windows system, internal or external storage media.

2. Roles and Permissions Requirements

To import PST files into Office 365, you need to assign the Mailbox Import Export role to the user account. This role is not assigned to any user or group, including the administrator.?

In addition, you should have the Mail Recipients role assigned in Office 365. These permissions and roles can only be assigned or granted by Office 365 global administrator. Otherwise, the import job will fail, and you will need to recreate a new job to import or migrate PST files to Office 365.?

3. PST File Size Limitation

Whether you choose Network Upload or Drive Shipping method, you cannot migrate PST files larger than 20 GB. Microsoft recommends uploading the PST files less than 20 GB to avoid performance issues. If a PST is large, split it into smaller files to keep the size under recommended limits. This may require you to export mail items to PST in two or more stages and then map the PST file accordingly in the PST import mapping file.

4. Command Line Tool to Upload PSTs

To import or migrate PST files using the Network Upload method, you need to upload the PST files using the Azure AZCopy tool. It’s a command-line interface-based tool that many users may not find convenient. You need to run specific commands to upload PST files stored in a local folder to the Azure Storage location via SAS URL.?

5. Performance Issues

You may encounter performance issues while importing large PST files in the Drive Shipping method. However, with the Network Upload method, you may encounter performance issues due to poor or unstable network connection, large PST files, bandwidth issues, etc. Some common issues that you may encounter are as follows:

• PST Import Stuck

Office 365 import service has a limited ingestion rate that prevents you from importing PSTs larger than 24 GB per day in a mailbox. Besides, the import service run in an environment that might be shared by other tenants, impacting the import job. This can result in a stuck or slow PST import. This usually occurs when the PST files are larger than 20 GB. In addition, the import process may get stuck if you try importing more than one PST file in the same mailbox.???

• Mail Items or PSTs Skipped

In the manual PST upload method, whether you use Network Upload or Drive Shipping method, the corrupted or bad mail items are skipped during the PST import in Office 365. You can see the skipped mail items in the import job status.

In addition, you may run the Get-MailboxImportRequest cmdlet to check the corrupted or skipped (BadItemsEncountered) mail items found in the PST files during migration. After import, you can download the report to view more details related to the import job.

• Import job Failure

You may encounter certain errors when the storage on the target server is lower than the data being imported. In this case, if the PST is larger than the available mailbox size, you may encounter the MapiExceptionShutOffQuotaExceeded error during the import job in Office 365. Thus, you must check the available storage in the mailbox before starting the import job.

6. Time and Cost

The drive shipping method to import or migrate PST files to Office 365 can take a few days or weeks. In addition, Microsoft charges $2/GB or $2000 for 1 TB cost for uploading and importing the PST file in Office 365.

During transit, the storage drive could get damaged if not packed or shipped securely. Moreover, if you want your hard drive back once PST files are uploaded to Azure Storage, Microsoft will charge you for shipping it back to you.

If you choose to upload the PST and then import it, it could take a few hours to upload PST based on your network connection and slightly more or less time to import the same PST into the Office 365 mailbox. For instance, a 2 GB PST took 1 hour 20 minutes to upload and 2.5 hours to import into the mapped Office 365 mailbox in our test. Of course, this may vary based on your network speed, bandwidth, PST size, etc.

7. Data Security and Compliance

When you ship a drive to one of the Microsoft data centers, the hard drive containing PST files may cross international borders. This can raise data security and compliance concerns. Thus, you must ensure that you ship the drive in accordance with data security laws.

Final Thoughts

Migrating PST files to Office 365 is a complex and tedious task that requires extensive planning and preparation to avoid performance issues, errors, and failure. In this article, we have shared the methods used to import and migrate PST files to Office 365 and the challenges associated with these methods. In addition to all the challenges we discussed, if you also have OST files that belong to deleted or removed user accounts—also known as orphaned OST files—you cannot export mail items from such OST files to Office 365 using any of those methods.

To avoid the issues and challenges associated with the manual methods, you can use an Outlook migrator tool, such as Stellar Migrator for Outlook . The tool migrates the mail items from both OST and PST files to Office 365 mailbox directly. The software allows you to migrate PST files as large as 50 GB without issues. Furthermore, it keeps the folder structure intact and migrates all mail items with complete integrity and precision. Besides, it’s a GUI-based tool that anyone can use to quickly migrate PST files to Office 365 with secure Microsoft Modern Authentication.