How can I confirm that each PST file is going to the correct mailbox?

Review the source-to-target mapping screen before starting the migration and manually correct any proposed match that does not reflect the migration inventory.

Can I import multiple PST files without Outlook installed?

Yes. The direct PST-to-Microsoft-365 migration workflow does not require Outlook to be installed.

Can I restore a PST file to an Online Archive or shared mailbox?

Yes, when the destination exists, is enabled where required, and the connected account has the necessary access.

What should I check if some PST items are missing from the target?

Review the migration log, filters, source selection, mailbox mapping, message-size limits, target permissions, and Microsoft 365 service conditions.

What happens if I run the same bulk PST migration again?

For supported re-runs from the same source/computer to the same target, EdbMails uses incremental migration tracking to avoid reprocessing items already recorded as migrated.

Can Microsoft 365 throttling slow a bulk PST migration?

Yes. Microsoft 365 throttling and service conditions can affect throughput.

Do I need Exchange Online impersonation rights for this migration?

Use the current EdbMails modern-authentication workflow. Older EWS impersonation instructions are not the current default for Exchange Online.

How should I verify a bulk PST migration?

Review migration logs and verify representative mailbox data in the target before retiring source PST files.

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How to Import Multiple PST Files to Office 365

When several users or departments have PST archives, the critical part of a bulk import is mapping every PST to the correct Microsoft 365 destination and verifying the result. This guide covers the EdbMails multiple-PST workflow from source preparation and target connection through mailbox mapping, migration, re-runs, and post-migration validation.

With the EdbMails PST Migration Tool, you can add multiple PST files to one job and map them to primary, shared, archive, or other prepared Microsoft 365 mailbox destinations. EdbMails can suggest source-to-target matches, but review every pairing before you start—especially when PST filenames do not match target mailbox addresses.

Import multiple PST files to Office 365

EdbMails can import supported emails, attachments, contacts, calendars, tasks, notes, journals, folders, and available metadata from the selected PST files. After migration, review the EdbMails log for completed, failed, or skipped items and verify representative folders and mailbox data directly in Microsoft 365.

The steps below show how to add the files, connect to Office 365, check the mappings, and verify the restore.

Bulk PST to Office 365 migration planning

Create a PST-to-mailbox inventory.
Record each PST filename, owner, approximate size, intended Microsoft 365 mailbox, and whether the destination is a primary mailbox, shared mailbox, Online Archive, or prepared Public Folder location.
Standardize source names where practical.
Clear PST filenames and a source-to-target inventory make automatic mapping easier to review and reduce the risk of importing one user's archive into another user's mailbox.
Plan the migration in manageable batches.
Large bulk imports can be staged by department, mailbox group, PST size, or business priority. Microsoft 365 throttling and service conditions can affect throughput, so avoid assuming one fixed completion time.
Keep source PST files until validation is complete.
Do not delete the only copy of a PST after the first successful run. Retain source files until migration logs and representative target mailbox data have been checked.

Before You Import Multiple PST Files to Office 365
1. Install EdbMails on a supported Windows computer that can reliably access the PST files. Outlook is not required for the direct PST-to-Microsoft-365 migration path.
2. Check that the target mailboxes exist and have the appropriate licenses. EdbMails includes an option for automatically creating Office 365 mailboxes and assigning licenses. If your team prepares the mailboxes manually, use these instructions:
3. Check that each destination has enough mailbox storage for the PST data you plan to import. If you still need to select licenses, compare Microsoft 365 business plans and enterprise plans for the target users.
4. If the destination is a public folder, create and configure the corresponding public folders in Office 365 before you begin.
5. If you plan to restore into an online archive, enable the archive mailbox for the target user first. Follow the steps to enable online Archive in Office 365.
6. Prepare the Microsoft 365 authentication method required by your EdbMails connection workflow. Use the current modern-authentication process shown in the application. If you use manual Microsoft Entra app registration, configure the required app permissions and administrator consent before migration. Legacy Exchange Online EWS impersonation guidance should not be used as the default connection method.
7. Important for current Exchange Online tenants: Microsoft began globally disabling Exchange Web Services (EWS) in October 2026 and plans full disablement by April 2027. Follow the current EdbMails modern-authentication workflow rather than older EWS impersonation instructions. See Microsoft's EWS deprecation guidance.
8. Review Exchange Online message-size and mailbox limits if the PST files contain large messages or attachments. Microsoft documents a 150 MB migration message-size limit for Exchange Online plans, while other tenant, mailbox, client, and service limits can be lower.
  See Exchange Online limits.
Steps to Import Multiple PST Files to Office 365
1. Step 1: Install EdbMails
  - Download and install EdbMails on the computer that can access your PST files.
    Check the EdbMails PST system requirements before installation.
2. Step 2: Launch EdbMails Software
  - Open EdbMails and enter your account email address and password. Click 'Login', or choose 'Start Your Free Trial' if you are evaluating the software.
  - Select ‘Office 365 Migration’.
  - Then choose ‘Restore PST to Office 365’.
  - Keep the default job name, or click ‘New Job’ and give this import a name you will recognize later.
3. Step 3: Add multiple PST files
  - Click ‘Add file(s)’ to browse for the PST archives you want to restore.
  - Select the PST files you want to include in this job.
  - Check the file list to confirm that it contains the intended PST files.
  - If you want each PST to appear under a folder named after that file, select the folder option shown below. Then click 'Next'. Review the resulting folder destination when you map the files.
4. Step 4: Connect to the target Office 365 tenant
  - Click ‘Add New Connection’ to connect to the target tenant. If you have already configured the connection, select it and click ‘Connect to Existing’.
  - Choose the target connection options that match your tenant setup, then click ‘Next’.
  - Use the connection method prepared in the prerequisites, whether automatic or manual app registration, and click ‘Login’.
  - Complete the Microsoft sign-in prompt for the target account.
  - After signing in, choose how to load the target mailboxes. If you have prepared a mailbox list, you can also load the mailboxes using a CSV file.
5. Step 5: Map source and target mailboxes
  - Choose automatic or manual mapping, then check which target mailbox is paired with each PST file.
    
    EdbMails can suggest source-to-target matches. Check the proposed pairings carefully, especially when a PST filename differs from the destination mailbox name. You can manually map source folders and subfolders to specific target folders when needed.
6. Step 6: Start PST to Office 365 migration
  - Once each PST is mapped to the intended mailbox and folder, click ‘Start Restore’.
  - When the job finishes, click ‘View Log’. Review the report for completed, failed, or skipped items. Then open the target mailboxes and check a sample of folders, messages, contacts, and calendar entries against the source PST files.

Bulk PST Migration Features in EdbMails PST Migration Tool

Bulk PST import: Add several PST files to one job and review the destination for each file before starting the restore.
Incremental migration: For supported re-runs from the same source/computer to the same target, EdbMails tracks items already recorded as migrated so completed items are not needlessly reprocessed. Review the log after every re-run.
Folder structure: Keep supported folders organized in the target mailbox. You can also choose to place imported content under a folder named after its source PST file.
Selective import: Use the available date, folder, or item-type filters when you need to restore only part of a PST file.
Parallel mailbox processing: EdbMails can process supported migration work in parallel. Actual throughput depends on PST size, bandwidth, system resources, Microsoft 365 throttling, tenant conditions, and service limits.
Modern authentication: Connect to Microsoft 365 through the supported modern-authentication workflow and your tenant's configured MFA and access policies.

Frequently Asked Questions

How can I confirm that each PST file is going to the correct mailbox?
Review the source-to-target mapping screen before starting the migration. Check the target mailbox and destination folder for every PST and manually change any proposed match that does not reflect your migration inventory.
Can I import multiple PST files without Outlook installed?
Yes. The direct PST-to-Microsoft-365 migration workflow does not require Outlook to be installed. EdbMails reads the PST sources and migrates supported data directly to the connected Microsoft 365 target.
Can I restore a PST file to an Online Archive or shared mailbox?
Yes, when the destination exists, is enabled where required, and the connected account has the necessary access. Confirm the destination mapping before starting the job.
What should I check if some PST items are missing from the target?
Open the migration log and look for failed or skipped items. Check filters, source selection, mailbox mapping, message-size limits, target permissions, and Microsoft 365 service conditions before running another pass.
What happens if I run the same bulk PST migration again?
For supported re-runs from the same source/computer to the same target, EdbMails uses incremental migration tracking to avoid reprocessing items already recorded as migrated. Review the log after each re-run.
Can Microsoft 365 throttling slow a bulk PST migration?
Yes. Microsoft 365 applies service throttling to protect availability. Throughput can vary with tenant conditions, PST size, bandwidth, concurrent work, and Microsoft service health, so large projects can require staged runs or additional time.
Do I need Exchange Online impersonation rights for this migration?
Use the current EdbMails modern-authentication workflow shown in the application. Older EWS impersonation instructions should not be treated as the current default for Exchange Online because Microsoft began global EWS disablement in October 2026.
How should I verify a bulk PST migration?
Review migration logs for every PST and target mailbox, then verify a representative sample of folders, messages, attachments, contacts, calendars, and item counts in Microsoft 365. Retain the source PST files until validation is complete.