Home » technologies » OST File is not Recognized by Outlook – Error Fix

OST File is not Recognized by Outlook – Error Fix

Anuraag Singh | Modified: 2021-10-20T13:13:18+00:00|technologies | 5 Minutes Reading

Microsoft Outlook users face different errors regarding OST and PST files and one of them is the “OST File not Recognized by Outlook” error. In this error, you can not open your OST file in your Outlook application. It’s kind of a really hectic situation when this error appears in between your work.  

OST file is not recognized by Outlook

Reasons of OST File not Recognized by Outlook:-

There can be different reasons for this error:-

  1. The main reason is corruption in the OST file. Outlook will not recognize the OST file when the OST file is severely damaged.
  2. The error appears when the Exchange server does not match the OST file size with the mailbox file size.
  3. The synchronization error between the OST file and Exchange server. Microsoft Outlook is unable to recognize the Outlook OST file.
  4. Sometimes the OST file exceeds the size limit which causes the performance disturbance in Outlook. 

 Scenarios of “OST file not recognized by Outlook” Error:

There can be two scenarios where the “OST File not Recognized by Outlook” error appears:

Case 1: If OST files are already in your system but Outlook is not running and you try to use ScanPST.exe to restore your OST file. The tool shows you a dialog box in which this error is written.

Case 2: This error can appear in your Outlook application when you try to open your application. In this situation, you can not use your Outlook until you solve this error.

Methods to Fix OST File not Recognized by Outlook:-

It is difficult to work on Outlook with a damaged OST file. Users have to take quick steps to remove that error. You can take the given below approaches to remove the above-mentioned error:-

Method 1: Update Microsoft Outlook 

  • The simplest method you can use is to Update your Windows and Microsoft Outlook & Restart your PC. 

Method 2: Recreate OST file

You can recreate the OST file, it would help you to fix the error.

(Close your Microsoft Outlook if its running- for both options)

Directly Rename your OST file

  • Go to your OST file location (C:\Users\admin\AppData\Local\Microsoft\Outlook)
  • Now rename your OST file
  • Then open your Microsoft Outlook and your OST file will automatically be created.

Enable Use cached exchange mode to recreate the OST file 

  • Control Panel >> hit Mail option.
  • Mail Setup dialogue box >> hit Show Profiles >> your profile >> choose Properties.
  • Choose an Exchange account email  >>  Change,  
  • Go to More Settings >> Advanced >> enable Use Cached Exchange Mode.
  •  Apply >> Ok >> Next >> Finish

Method 3: Use Outlook Inbox Repair Tool 

NOTE: In case you didn’t use this tool

  • Close your Outlook application
  • Open Control Panel >> hit on file Explorer options >> view
  • Hit Show hidden files, folders, and drive.
  • Search ScanPST.exe or exe.
  • Or you can Go to >> DriveC:\Program files\Microsoft Office\Office15 (for windows 10), Office12, Office14 (respectively for windows 7 & 8)

Use this tool to get to know if your OST file is highly corrupted or not. because this tool can only restore minor corruption in your OST files.

You can use Outlook Tool 4-5 times until it shows you NO ERROR in the OST file but if it still shows you the error “OST file not recognized by Outlook ” that means this tool can not recover the OST file.

In case, Outlook repair tool is not working then you will require software. Because the OST file might be highly corrupted and then there is no manual method to recover the OST file. You need to convert that corrupted OST file while maintaining its header and format into a PST file.

So basically, if you really want to remove the corruption and view your OST file, you will definitely need another tool to convert the OST file because Outlook does not provide you converting feature. Without software, it’s impossible to open an OST file. There is no manual method of opening and converting an OST file. You can install OST to PST converter developed by SysTools.

Method 4: How to Use this Software

Download Tool Purchase Now

  • Install Software in your system 

main screen

  • Open it >> select ADD files

add file

  • Add your OST File Location >> Add

add ost file

  • Now hit on Export 


  • Set the Destination of your Export file >> hit on Export.

add location

  • Go to your Export file location and open them with Microsoft Outlook.

Merits of Using SysTools Software:

Apart from its safe and secure score, SysTools provide many benefits in converter some of them are:-

  • Supports  every version of Outlook (2019, 2016, 2013, 2010, 2007, etc)
  • OST files can convert in PST as well as EMLX, EML, MBOX file extensions.
  • Easily convert large size, orphaned, or inaccessible OST  file.
  • Export OST file data with full accuracy.
  • Also export in PDF, HTML, DOCS, TXT, etc, other formats.
  • The free demo version is available.

Final words:

So in this article, we discuss the error “OST file not recognized by Outlook” and how this error appears. I hope you solve your problem with the given methods.

Also, read Set of folders cannot open in Outlook