Why Does Importing PST to Office 365 Fail or Get Rejected? Hidden Reasons Revealed

You have made all the preparations and pressed the Import button to begin the process. But the results are job failures or rejection which is completely different from your expectations.

The blog will save you from long procedures like hit & trial to handle the issues appropriately. Just stick to the guide, and get to know the common PST import issues in Microsoft 365 and their relevant solutions till you reach the very end.

Basic Overview: How Does Microsoft 365 Import Service Actually Work?

If you want to troubleshoot PST import errors in Microsoft 365, then understanding the procedure becomes crucial. Check out the section below for the same purpose:

Office 365 provides two ways to import PST files on Exchange Online:

• Network Upload: You upload the PST file to an Azure Storage container with the help of the AzCopy tool and a temporary access key.
• Drive Shipping: In this method, a hard drive is physically mailed to a Microsoft data center.

The import service is not dedicated to a single organization. It operates in an environment shared across many Microsoft 365 tenants at once. That's the main cause behind the slow speed of the import process.

List Of 6 Hidden Reasons Why PST Import Failed Or Rejected

In the section below, we have highlighted some of the main reasons that may be the reason behind the PST import failure or rejection. Explore them now to avoid PST import fails in Microsoft 365 scenario:

Cause 1. Your Tenant Is Competing for Shared Import Bandwidth

Microsoft cited a 24GB per day per mailbox import speed, but this number is an average, not a promise. It is because the service works on shared infrastructure and completely depends on the particular day when you are running the job.

If your job looks "stuck" but hasn't actually errored out, it doesn't mean the file is broken. This can happen even when nothing is technically wrong with your file, your mailbox, or your configuration.

Here are the solutions to fix it:

• Judge progress against elapsed time and file size.
• Schedule large migrations during the off-peak hours.
• Open the job status page and confirm that it is marked as running.
• Continue the job if it is active rather than canceling or restarting it.

Cause 2. The PST File Is Bigger Than the Practical Limit

Another reason might be that the size of your PST files exceeds the threshold limit of 20 GB per file. As a result, the import duration stretches out, and the chances of a stalled job increase significantly.

So, split the PST files into smaller parts before the migration to avoid size-related issues. Smaller files will import faster and fail less.

List of solutions to fix it:

• Check the file size of all the PST files before upload.
• Remove the unnecessary items before you split files.
• Split the PST file that exceeds the 20 GB predefined limit.
• Finish the already ongoing job of uploading oversized PST files.

Cause 3. Corruption or Damage In the Uploaded PST Files

For a smooth PST import job, the files must be healthy. If corruption is found, then the damaged items will be skipped automatically. As a result, you see "Items skipped (corrupted)" under the job status page.

Fix these issues using the solutions below:

• Run PowerShell to get the exact bad items count.
• Use the Inbox Repair tool if the count is higher than expected.
• Upload the repaired PST file to the same Azure storage location.
• Create a new import job for the repaired file with the same target folder.

Cause 4. The Target Mailbox Ran Out of Room Mid-Import

A frustrating error that only appears when you start the import job. This error indicates that you need to shut off the job because of exceeding quota. It means the imported data is larger than the available space in the destination mailbox.

To avoid this, apply the provided solutions:

• Remember the 100GB limit applies to archive mailboxes and the auto-expansion will not work in the import or migration scenarios.
• Contact the Microsoft support team to review the mailbox quota if you actually need it.
• You can delete or archive unnecessary data in the target mailbox before uploading PST files.
• Compare the total size of the PST file against the actual free space in the target mailbox before import.

Cause 5. The Import Service Isn't Rolled Out In Your Region Yet

Microsoft releases the Import service in phases across regions rather than everywhere at once. Also, local data transfer or data residency regulations restrict the service operation in that specific region. Mainly, the issue isn't related to the subscription plan.

Necessary measures you can take in that scenario:

• Switch to professional solutions for larger mailbox migration.
• Use the manual Outlook import feature for small and urgent migration.
• Ask specifically about the timing issues or regulatory restrictions if not available yet.
• Contact Microsoft support or reseller to confirm the availability of the import service availability in your region.

Cause 6. The 30-Day Azure Upload Expire Nobody Warns You About

Azure storage container stores the uploaded files for 30 days. After that, they get deleted when the most recent import job is created for your tenant. Within that window, you have to complete the import process, or the files are gone forever.

Apply the solutions below to fix it:

• Check the original upload data against today's date.
• Reupload the PST files to the Azure storage location if it's been more than 30 days.
• Create the new import job immediately after the reupload is completed instead of leaving it for later.

Key Takeaways

Here, we have learned about the common PST import issues in Microsoft 365 that you may encounter. By knowing the hidden reasons, you will be able to tackle the suddenly appeared issues with suitable yet effective approaches.

Most of the issues will be resolved with the native solutions, but you need careful consideration throughout the process. You can avoid them by using professional solutions like Recoveryfix Import PST to Office 365 tool. The software simplifies the entire process for both technical or non-tech users.