Fix The Connection to Microsoft Exchange is unavailable, Outlook must be online or connected

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Isn’t it always boring when you make a mistake? And it’s especially annoying when the bug is mysterious and doesn’t tell us the cause of the problem. Well, “The connection to Microsoft Exchange is unavailable” is such a mysterious message that does not tell you why there is no connection.

If you are like me, you will probably review the different possibilities in your head and try to find the most likely cause of the problem. If you see this error message, try one of the following options and I hope one of them will fix it for you.

Modify Registry

registry editor - Another installation is in progress in Windows 10

The connection to Microsoft Exchange is not available error usually appears due to problems with your registry. Your registry contains the necessary information that Outlook uses to access Microsoft Exchange, and if this information is not present in your registry, you receive the error message Connection to Microsoft Exchange is unavailable.

To solve this problem, you must manually add the required data to the registry. Changing the registry can be somewhat dangerous and can cause some problems if you don’t do it properly, so be careful and save your registry just in case.

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Users reported that they had solved this problem by copying the registry key from a working PC and adding it to their registry on the problematic PC. To do this, follow the steps below:

  1. On the workstation, press Windows + R and type regedit. Click OK or press Enter.
  2. When the Registry Editor opens, go to the HKEY_CURRENT_USER\Software\Microsoft\Windows\Windows\CurrentVersion\ExplorerUser Shell\in the left panel.
  3. Right-click the User Shell Folders button and select Export from the menu.
  4. Select the export location for this key, enter a name, for example export.reg, and click Save.
  5. Locate the export.reg file and copy it to the problem PC.
  6. Then simply run the export.reg file on the problematic PC and it will be added to your registry.

Create a new alias

A common way to solve this problem is to create a new alias in Office 365 and use this alias to configure your Outlook.

To do that:

  • Log in to your Exchange Administration Center.
  • Navigate to the recipients -> mailboxes and click on your mailbox.
  • Then select the e-mail address and click on the “+” sign.
  • Select the SMTP server and add a new alias to your domain.
  • Use the new alias instead of your email address to configure your Outlook.
  • Finally, when prompted to enter your credentials, use the original Office 365 email address and it should work.

Flush your DNS

A kind of hiccup with the DNS of your computer may also be responsible for this problem. Fortunately, the DNS of a Windows computer can easily be flashed. To empty the DNS from your computer, it’s simple:

  1. Open the Start menu.
  2. Look for “cmd”.
  3. Right-click on the search result labeled cmd or Command Prompt and click Run as Administrator to launch an advanced command prompt with administrator privileges.
  4. Type the following in the high prompt and press Enter :
    ipconfig /flushdns
  5. Close the highlighted prompt.

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