Summary: Outlook 365 is an Office 365 product and a cloud-based email client that works with Exchange online. It offers several features and advantages over the standalone Microsoft Outlook version for Windows and Mac, such as better security, secure cloud storage, compliance protection, automatic upgrades, etc. In this guide, we’ve discussed a manual and an automated method to help you import OST files into Outlook 365 accounts.
OST or Offline Storage Table, also known as Offline Outlook data file, is used to store an offline copy of Exchange mailbox items. Unlike PST, you can’t import an OST file into Outlook 365 as the file is encrypted with the MAPIEntryID GUID key.
Although you can export the mailbox items from an OST file to PST format via Outlook Import Export wizard, the problem arises when the OST file is orphaned or inaccessible. It means the OST files that belong to a deleted or disabled Exchange mailbox profile.
However, you can extract the mailbox items from inaccessible or orphaned OST files and export them directly to Outlook 365 account by using an OST to PST converter software, such as Stellar Converter for OST. The software also helps you convert multiple OST files simultaneously to corresponding PST files that you can import into Outlook 365 accounts.
Table of Contents
Below are the two methods to import mailbox items from an OST file into Outlook 365 with 100% integrity and without the risk of any data loss.
This method is divided into two steps. First, you need to convert the mailbox items from OST to PST by using Outlook Import/Export wizard. Then import the converted PST file into Outlook 365 account.
NOTE: This method works when the Outlook profile and OST file are in sync with the mailbox on the server. This method won’t work if the Exchange server is offline or the Outlook profile is not connected to the server. In such a case, you can follow the next method to convert and import the OST file into Outlook 365.
Now you can import the converted PST file, containing OST mailbox items, into your Outlook 365 account via the Office 365 Admin Center. However, you must assign the Mailbox Import Export Role to the user account before you can import the PST file.
To assign Mailbox Import Export Role, follow these steps:
Wait for an hour for changes to take effect. However, it may take up to 24 hours for changes to take effect.
Now you can import the converted PST file into Outlook 365 account via the Office 365 Admin Center.
At this stage, you have successfully imported the converted PST file into your Outlook 365 account. If you have multiple OSTs to import, you will be required to export each into a PST file and then perform the manual steps described above to import the PST file.
To shorten this process and import the OST file into Outlook 365 directly, you can follow the next method.
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To import the OST file into Outlook 365 directly, you need Stellar Converter for OST software. This advanced OST to PST converter software can extract the mailbox items, such as emails, contacts, attachments, calendars, notes, etc., from an OST file and export them directly to your Outlook 365 account. All you need is valid credentials of the destination Outlook 365 account. There is no need to assign special roles and permissions to import the OST file into Outlook 365.
The steps are as follows:
The software also allows you to convert multiple OST files to PST format via the Batch Conversion option.
After conversion, you can create a CSV file to map and import the PSTs into Outlook 365 or Office 365 accounts as discussed in Step 2 in Method 1.
Below are the key differences between the two approaches to import OST files into Outlook 365.
Manual Method | Automated Method |
The lengthy process with multiple steps to import OST into Outlook 365 | Exports OST to Outlook 365 in a few clicks |
Does not work when the OST file is inaccessible or orphaned | Converts inaccessible or orphaned OST files to Outlook importable PST files |
Exports OST mailbox items to a single large PST file | Provides the option to split and save mailbox items into multiple PST files (based on date range and size) to avoid corruption and performance issue |
Exports mailbox items from one Outlook profile or OST file to PST at once | Features batch conversion option to convert and export multiple OST files to PST format |
No option to directly export OST mail items to Office 365 | Option to import OST mail items directly to Office 365 (Outlook 365) or live Exchange Server |
Takes significantly longer time to export PST | Efficiently extracts and saves mailbox items from OST file to PST |
An OST file can’t be imported into Outlook 365 account as it is encrypted and binds to an Outlook MAPI profile. To import mailbox items from an OST file into Outlook 365, you must convert the OST file to PST format. This can be done via the Outlook Import Export wizard. However, the wizard works when Outlook profile and OST file is accessible. To convert and import inaccessible or orphaned OST files, you must use an OST to PST converter software, such as Stellar Converter for OST.
The software helps you skip multiple steps required to import the mailbox items from an OST file to Outlook 365 manually. It can directly import OST files into Outlook 365. All you need is valid user credentials of the Outlook 365 account. It also helps you convert multiple OST files to PST format via Batch Conversion. This allows you to migrate multiple OST mailboxes to Outlook 365 with minimal effort and time.
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