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Frequently Asked Questions


What is DataNumen Exchange Recovery?

DataNumen Exchange Recovery(DEXR) (formerly DataNumen Exchange Recovery) is the best recovery tool for Microsoft Exchange offline storage(.ost) files. It uses advanced technologies to scan the orphaned or damaged offline storage files(.ost) and recover your mail messages, folders, posts, appointments, meeting requests, contacts, distribution lists, tasks, task requests, journals, notes, etc. in them as much as possible, thereby minimizing the loss in data disaster.

Which type of Microsoft Exchange offline storage(.ost) files can DataNumen Exchange Recovery recover?

DataNumen Exchange Recovery supports to recover Offline storage(.ost) files for Microsoft Exchange 5.0 to 2019, Outlook 97 to 2019 and Outlook for Office 365.

How can I determine whether DEXR can recover my Microsoft Exchange offline storage(.ost) file successfully, according to the results generated by the demo version?


Please just use the demo version to recover your Microsoft Exchange offline storage(.ost) file normally in "Recovery" tab. After the recovery process, a new recovered PST file will be generated and you can use Outlook or other compatible mail clients to open and browse the recovered messages and other items in it. Please note for the demo version, the actual contents in the messages and other items are replaced with demo information. You need to purchase the full version to get the actual data.

According to these information, you will know whether DEXR has worked successfully on your damaged file. If the repair was successful, then please order the full version to get the actual data in the messages and other items.


When I start the recovery process, I get the error message "Either there is no default mail client or the current mail client cannot fulfill the messaging request. Please run Microsoft Office Outlook and set it as the default mail client." and DataNumen Exchange Recovery quits at once. How to solve this issue?


DataNumen Exchange Recovery requires Microsoft Outlook to be installed and set as the default e-mail client on the computer.

To solve this issue, please:

  1. Install Microsoft Outlook on your computer if it has not be installed yet.

Set Outlook as the default e-mail client on the computer. To do this, follow these steps:

  2.1 Start Microsoft Internet Explorer.

On the Tools menu, click Internet Options.


Click the Programs tab.


In the E-mail box, click Microsoft Outlook.

  2.5 Click OK to close the Internet Options dialog box.

Restart DataNumen Exchange Recovery to recover your OST files.


When recovering the OST file, I get the error message in the recovery log "Error 6: Cannot create destination PST file. xxxxxxx. If you have Outlook 2000 or earlier versions installed, please make sure it is installed in the Corporate or Workgroup mode. For Outlook 2002 and later versions, please make sure Exchange Server components are not installed on the current computer. You may also refer to the faq in the help document for the detailed information.". How to solve this issue?


This error occurs when the MAPI subsystem on your computer is not installed or configured correctly. Please refer to "error 6" in DataNumen Exchange Recovery help document for more detailed information and solution.


When repairing a file under Windows 10, I get "DEXR.exe has stopped working". How to solve the problem?


If Microsoft Outlook is not installed on your system, you will get this error. Please install Microsoft Outlook on your system and then try again.

Alternatively, you can find another computer with Microsoft Outlook installed, then install and run DataNumen Exchange Recovery on that computer.


I failed to recover my Microsoft Exchange offline storage(.ost) file with DataNumen Exchange Recovery?


Contact with our technical support: . If possible, please also save the recovery log into a file(make sure the "Include System Information" option in the save file dialog is selected) and attach it in your e-mail.


How can I order the full version of DataNumen Exchange Recovery?


The demo version will output a recovered PST file containing all the recovered messages and other items, with the actual contents in them filled with a demo information. To get the actual data in the messages and other items, you need to order the full version. The price for the full version (single license) is USD 199.95.

Please click here to order now or get more ordering and payment information. We accept all major credit cards, Maestro (UK), giropay (Germany), iDEAL (Netherlands), Bank/Wire transfer, WebMoney, Purchase orders, PayPal, Checks and Direct Debit.

If your company or institution is interested in licensing DEXR for several users, you can save a lot of money by purchasing a volume license.


What happens after I send in the order?

In general, you can download the full version of DEXR immediately after sending the online order form.

If you do not get your full version... or if you've lost it (Hey, it happens! :) ... please email us at . Please include your name, address, email address, and order confirmation number (if you have it).
    We will be happy to help you.