How to Import PST to Office 365 Without Duplicates; A Stepwise Solution to Follow

Import PST to Office 365 Without Duplicates

Mohit Jha | Modified: February 24, 2023 | Office 365 | 7 Minutes Reading

Do you feel the need to import PST to Office 365 without duplicates? The duplicates are of course the cause of consuming unnecessary space. These even hurt more when we want to migrate our data from Outlook to Office 365 and the process is taking too long due to these duplicated items.

Eventually, the duplicates might lead to serious issues if not removed timely. So, let us discuss how to import PST files from MS Outlook to Office 365 with the help of manual as well as Office 365 PST MigrationTool, avoiding duplicated items.

How to Import PST to Office 365 Without Duplicates?

As a matter of course, we have two kinds of PST files. One is orphan PST and the other is already configured PST in Outlook. So we will learn how to import both kinds of PST files into Office 365 in the further section.

So first we will remove the duplicates from the orphan PST file using the Import/ Export function of Outlook. To do so, first, we will import duplicated data from PST file into Outlook and then Export it.

Note: Orphan PST is a PST file that resides in some location other than MS Outlook in your system. It needs to be imported to Outlook.

5 Quick Steps to Import PST to Office 365 Without Duplicates

  • Step 1. Download, Install & Run Software.
  • Step 2. Login with Office 365 Admin/User Credentials.
  • Step 3. Add PST Files/Folders & Authenticate Them.
  • Step 4. Choose Required Mailbox Items to Import.
  • Step 5. Apply Date Filter & Click on Import.

Import / Export PST File Avoiding Duplicates

If you have to import a PST file to Office 365 which is not imported into Outlook but is located in some other location in your system, then first import it to MS Outlook to avoid duplicates. And if you want to migrate an already configured PST inside Outlook to Office 365 then skip the first step and jump to step 2 to Export PST.

Import PST into Outlook

Follow the given below steps to import PST into Outlook:

  • Open MS Outlook >> Go to File
  • Now choose Open & Export option >> select Import/Export
  • Now choose Import from another program or file option inside the Import/Export wizard.
  • Click Next
  • Choose Outlook Data File (.pst) option >> tap Next
  • Now browse the location of the PST file and select the option Do not import duplicates >> Finish

Important Tip: The option “Do not import duplicates” is used to prevent all the duplicates in the PST file that we are importing into Outlook.

Also Read: How to Export Office 365 Mailbox to PST via PowerShell 

The duplicate free PST file has been imported into Outlook and now you have to export it so that you will further migrate it to Office 365.

Export the Duplicate Free PST File

  • Open Outlook >> go to the File option
  • Choose the Open & Export option >> tap on Import/Export option.
  • Click on “Export to a file” >> hit Next
  • Now choose the folder to export from and click Next
  • Next, browse the location where you want to store your exported PST file >> hit Next

The above steps are for Outlook 2013 version. To know the Import/Export steps for other versions, refer to this article:

Now you have a duplicate free PST file and you have to import it to Office 365. Let us see which methods can be used for the same.

Techniques to Import PST to Office 365 Without Duplicates

There are 3 genuine methods to import PST to Office 365. Manual, as well as automated ways, can be used to upload an Outlook PST file to O365.

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Method 1. Import PST to Office 365 Without Duplicates Using the Tool

The most secure and fast solution for the migration of PST is using the above-mentioned tool. Here are all the steps to use in the tool to upload PST into Office 365 with Admin Account.

Step 1. Download & Run Office 365 Import PST tool.

Step 2. Now mark the check “Is Office 365 Admin” option >> press Login button >> click Add Files / Folder button.

add PST file

Step 3. Now browse the PST file (single file or entire folder) >> click on Open

Browse Outlook data file

Step 4. You will get a list of all the PST files, and enter the Office 365 email addresses mapped with files.

enter correspondent address

Step 5. Now enter the credentials for domain ID & authenticate.

Step 6. You also get the filters like Date Filters, and calendars. Select accordingly.

include folders

Step 7. Now check the “Include Folders” check box and enter the folders that you want to mention for PST to Office 365 migration.

Date filters

Step 8. You will get multiple options like:

  1. Attach Outlook PST file: to make a folder including PST name & add more folders
  2. Incremental import: To avoid duplicity of data w.r.t any previous migration
  3. Exclude Deleted Items & Exclude Sent Items: mark it checks

select multiple options

Step 9. Now click on the Import button.

Step 10. The process will start, and after completing it, click Save Report.

Method 2. Network Upload

Network upload is a manual way to import PST to Office 365 without duplicates. On a cloud, the user has to add PST files through the network. Although it is an effective method but slightly complicated and lengthy to run. The user will need Azure AzCopy software for this purpose and then proceed further.

Also Read: Migrate Distribution Group to Office 365 Safely – Comprehensive Guide

Method 3. Drive Shipping

This approach is also a great solution to migrating PST to Office 365 without duplicates. Here, you have to copy the PST files onto a hard drive encrypted with BitLocker. Then you have to ship it physically to the Microsoft Data Center. Now, again this manual way is way more than time-consuming to implement,  and expensive too. However, according to convenience, users can use this method.

For info about Drive Sipping refer to this article:

Pitfalls of Manual Methods to Import PST to Office 365 Without Duplicates

Manual methods are available to users but these have some serious pitfalls. To perform all the steps accurately, the user must have good technical skills otherwise any small mistake in the attempts might lead to data loss.

These methods are very lengthy and time-consuming. Users need to keep a lot of patience while performing manual techniques. Especially, when one is in a hurry to migrate Outlook data files to Office 365, it is not a good idea to opt for manual techniques.

For huge data, manual methods might be a bad decision to opt for. Both data loss and time consumption can be encountered for huge data file migration.

Must Read: How to Import PST to Outlook 365 Web In Few Steps? Everything You Need to Know


After analyzing all the ways to import PST to Office 365 without duplicates, the manual methods seem to be quite complicated and for a naive user, it can be pretty difficult to adopt these manual techniques. Moreover, the manual method has its own limitations and shortcomings.

On the other hand, the above tool seems to be a sophisticated and safer solution to import PST to Office 365 without duplicates instantly. Now, it is up to the user, what they use, but they must be aware of losing crucial data if they follow the manual method.