How to fix ‘Exchange Server is Unavailable’ error

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Summary: The error ‘Exchange Server is Unavailable’ can be encountered in any of the Exchange Server editions including 2007, 2010, 2013, or 2016. Thus, if you are one of the victims of getting such error, you can refer this blog to fix the error using the manual as well as automated solutions.

While working on MS Outlook, you may come across an error says ‘Exchange Server is Unavailable’. However, sometimes, the error gets resolved on its own but may be occurred later. In results, MS Outlook may stop responding and you cannot access mailbox items and other data stored in it. Hence, it’s very important to fix this error to keep you safe from a huge data loss disaster situation.

Before heading towards the solution that can fix the above-stated error, know the possible causes that result in this error.


Possible causes for getting ‘Exchange Server is Unavailable’ error

There might be several reasons for getting this error. Few of them are discussed below:

  • Poor or slow network connection: Poor or slow network connection causes Exchange Server inaccessibility issue.
  • The wrong configuration of Outlook profile: If MS Outlook profile is wrongly configured, the connection between Outlook and Exchange Server may not get properly established.
  • Network connectivity issue: Another reason for the abnormal behavior of MS Outlook is network connectivity issue.

Fix ‘Exchange Server is Unavailable’ error

Few manual solutions are there to fix ‘Exchange Server is unavailable’ error.

  1. Modify Registry settings
  2. Check for ‘read-only’ mode

Let us explain each one in detail:

Solution 1: Modify Registry settings

  • Go to Run by pressing a Windows+R key, type Regedit and click on OK button.


  • In Registry Editor, click on Yes to make a change to your device. It will lead you to the Registry Editor pane.

re pane

  • Here under Computer, double-click on HKEY_CURRENT_USER to expand and then select Software.


  • Now, move to Microsoft then Office>Outlook>RPC.
  • In File, move to Edit>New>DWORD and type DefConnectOpts and click on Enter button.
  • Finally, right-click on DefConnectOpts and click on Modify to give value 0 and click on OK.

Solution 2: Check for ‘read-only’ mode

Most of time MS Outlook users prefer to set Outlook Data File in read-only mode intentionally or unintentionally. However, it should not set as read-only mode. Furthermore, to confirm whether Outlook Data Files are set as a read-only mode or not, you need to know the location of Outlook Data file.

For PST Data file: C:Users<user_name>AppData >Local > MicrosoftOutlook

For OST Data file: C:Users<username>AppData >Local > MicrosoftOutlook

Note: The location of Outlook data file may vary among different OS.

An automated professional solution

If your Exchange Server turns in dismounted stage due to “Exchange Server is Unavailable” error, then you can opt for Exchange OST Recovery tool as you need to access your Exchange OST files in some other file formats. It provides facility to convert OST file to PST or some other file formats without altering its original data. It offers a smooth and secure conversion of OST data without any data loss.


In this blog, we have discussed both manual and automated solution to fix “Exchange Server is Unavailable” error. However, if you want a hassle-free process to fix this error, I will recommend automated Exchange OST Recovery tool over manual solutions.

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