Here are few methods on How to fix the error “The connection to Microsoft Exchange is unavailable. Outlook must be online or connected to complete this action” when opening Outlook.
Method 1 of 3: What we are going to do to fix this problem is remove Outllook Profile and add it again.
1. Exit Outlook.
2. Go to Control Panel, Select Small icons from the View by: drop down and select Mail.
3. Click Show Profiles, from the Mail Setup Window.
4. Click Add if you don’t want to delete the existing Outlook profile. If you are adding a profile make sure to select Always use this profile and select the new profile from the dropdown.
Note: keep in mind by deleting the existing profile it will delete any existing mailboxes in case you have more than one email set up with outlook. In my case I deleted the profile because I dont have any mailboxes set up.
5. Select the Outlook profile and click Remove button.
6. Once You have removed the old profile click on add… button to create a new one or you could run the outlook program in both method you’ll be prompted to create and name your new Profile. Type a name for the profile, then click OK.
7. You’ll immediately be prompted to enter your Microsoft Exchange email credentials, once entered click on next and that is it.
Method 2 of 3: Restart the Microsoft Exchange System Attendant service.
If the instruction above didn’t work Start/Restart the Microsoft Exchange System Attendant service on your Exchange Server:
1. Press the windows key plus R, to open the Run window and type services.msc, and then click OK.
2. In the Services window, locate the Microsoft Exchange System Attendant service in the details pane.
3. Right-click the service, and then click Start. If its already started stop it and re-start it.
Method 3 0f 3: Re-install Outlook or Microsoft Office.