What is NST File Format ?

Guide to Learn All About What is Office 365 NST & Outlook.nst File

Outlook NST File Extension

Microsoft Outlook users are aware about the PST as well as OST files. But, they are not familiar with the term ‘NST’, which is also a storage file in MS Outlook 2016, 2013, 2010 & 2007. Therefore, in this blog, we are going to discuss about this .nst file extension of Outlook with its creation, .nst file location, etc. You can also preview data stored within NST File with the help of NST Viewer Tool.

What is Outlook NST File Format ?

An Office 365 NST file or .nst file extension is automatically created in Microsoft Outlook 2016, 2013, and all below versions when an individual configures the Office 365 account in Outlook. After configuration, Outlook synchronizes Office 365 group cached local copy in a new separate file named as GST or Group Storage File. It let users access Office 365 group in offline mode as OST works for mailbox folders. This GST and OST file are stored in same the folder on the local machine.

The amount of data synchronized in GST (using .nst as a file extension) is controlled or managed by Outlook slider. This GST with .nst file extension (also called as NST of Office 365 groups) stores only calendars and group conversation in it. Apart from this, shared mailbox and other mailbox folders can normally be accessed from OST file stored on the local machine.

Can I delete Outlook NST file from my local machine?

"Recently, I have noticed that my hard drive storage is reaching its maximum limit. So, I checked the files stored on it. There is an Outlook.nst file, which is 5 GB in size. I do not understand, what file it is or what data it stores? Can I delete this Office 365 Outlook NST file or it contains some crucial data? Yesterday, I configured Office 365 account in my Outlook 2016. I think while doing so this O365 .nst file is created. So, can anyone tell me about this file? Is it ok to delete it from the local machine?"

If a user wants to access Office 365 Groups in Outlook, it needs to be configured in cached Exchange mode. The reason behind it is that only cached mode let users work in offline with group conversations. But, keep in mind that users cannot access the group document library unless you have a cached local copy available locally. So, when users find out this new file extension (.nst) with large size, they get confused. They think of deleting it as GST with .nst extension occupied a large amount of storage space. But, now it is clear that this NST file stores Office 365 group cached copy on the local machine.

How Outlook NST File Gets Created?

The file gets originated when users have configured their Office 365 account id with Outlook program. Following steps will help one in creating an Office 365 NST file in Outlook 2016 :

  • Open the Outlook Add account Wizard on your PC and mention the Office 365 email id within it
  • Outlook Wizard
  • Outlook starts preparing itself to add a new account to it displaying message "We're Getting Things Ready"
  • Outlook preparing
  • A message screen drops down in which you have to Enter the password of your O365 account. Click on the OK
  • Outlook message
  • A dialog box will appear in which you have to click on OK. This will continue the procedure of creating Office 365 .nst file in Outlook 2016, 2013, 2010 & 2007
  • Continue Step
  • When ‘Account setup is complete’ wizard appears, click on OK button
  • Account setup
  • The Outlook starts retrieving mailboxes from the configured account. This step might consume huge time because it is totally dependent upon the amount of data saved in the Exchange Online account.
  • Retrieving messages
  • When the data gets completely downloaded in Outlook, all things with your configured O365 email id appears. At this stage, you are done with the creation of .nst file extension in Outlook 2016
  • download completed

Outlook NST File Location

The location of NST file format is same as of the OST file path. One can take reference of following steps to learn the Outlook NST file location :

  • Right click on the Office 365 id configured in Outlook and Select Data File Properties option
  • Select Data Properties
  • Click on the Advanced button in the current wizard
  • Advanced Button
  • A Microsoft Exchange window appears in which you have to click on Advanced tab >> Outlook Data Settings
  • Data Settings
  • Copy the location, which is displayed in File box and then, Click on OK to close the current dialog box. Close all the Outlook screens and Open Windows Explorer
  • Copy Location
  • Paste the copied file location on the text box of Windows Explorer and remove last part till ‘Outlook’ word (as per shown in the figure). Press Enter to finally get Outlook NST file location
  • Path File
  • Just above the OST file of your O365 account, you will find the required Office 365 .nst file. The NST file format encountered till now will be in healthy state. But, since this file is saved locally on a machine therefore, there are high chances of the corruption. Therefore, in the upcoming section, we are going to discuss solution on how to fix NST file corruption.
  • NST File Location

A Reliable Solution to Deal With Corrupt NST Files

The procedure involves renaming of .nst file extension with .ost and then, browsing this file directly in the SysTools Recovery program. This repairing application will be fixing all corruptions from OST & NST file format and will provide several options to save recovered data. Users can take help of following steps to rename Outlook.nst data file with .ost file extension :

  • If opened then, close all the Outlook related programs and processes. After this, navigate towards the path where corrupted NST file is located
  • Close Outlook Program
  • Right-click on this NST file and click on Copy option. When the file gets copied, Paste it somewhere else on the different location of your PC, say desktop
  • Copy & paste NST File
  • Again, Right-click on the pasted file and Select Properties option
  • Select Properties
  • Change the .nst file extension with .ost and then, click on OK to update the changes
  • Chnge NST File Extension to OST
  • Finally, an OST file is created that you can browse within the Tool as mentioned Below :
  • Run Tool
  • Open SysTools Recovery software on your PC and click on Add File button. Browse .nst (renamed as .ost) file format , which is corrupted
  • Add File
  • Preview the data of your renamed NST file and then click on Export button
  • Click Export
  • Select all the recovered NST folders, which are to be saved again after file repairing. Then, choose the file format in which you want your resultant data.
  • Select File
  • Click on Browse button and choose the folder in which your extracted data files are to be stored. Click on OK when you are done with all this
  • Destination Location
  • At last, click on Export button to finally recover the data of corrupted NST file
  • Export File


Now, Outlook is no more limited up to PST and OST files. There is one more storage file within it i.e., NST. Very few technicians are aware from this file format. Hence, here we have described all details about What is Outlook NST File & Office 365 .nst file of Outlook 2016, 2013, 2010 & 2007. Also, we have covered the solution to deal with corrupted NST file Recovery so, that one does not faces any challenge whenever the user has to work with this file.