"Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders canot be opened. The attempt to log on to Microsoft Exchange has failed."

Hello vilibazmioo,

Good day!Thank you for reaching out to the Microsoft community.

I understand how frustrating it can be when you're unable to open Outlook, and I appreciate the steps you've already taken to resolve the issue. Based on the information provided, it seems you're encountering the error message: "Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The attempt to log on to Microsoft Exchange has failed." You've tried starting Outlook in safe mode, repairing the data files, and restarting your PC—all to no avail.

To better understand and investigate your issue,may I get some more detailed information from your side:

1. Will you please share me your Outlook version details? Please follow this article What version of Outlook do I have? - Microsoft Support and follow the steps to check.
2. Are you using Microsoft365 business account(@xxx.onmicrosoft.com/@yourdomain.com) or personal account (which is ended with outlook.com/hotmail.com/live.com/msn.com) or some other 3rd party pop/imap account?

3.Will you please share with me detailed error messages.

Let’s explore some additional troubleshooting steps that might help resolve the issue:

Turn off Compatibility Mode:

• Right-click the Outlook shortcut or executable file.
• Select Properties.
• Go to the Compatibility tab and ensure that "Run this program in compatibility mode for" is unchecked.
• Click Apply and then OK.

Reset the Navigation Pane

Sometimes the Navigation Pane settings in Outlook can become corrupted, leading to startup problems. To reset it, follow these steps:

• Press**Windows Key + R** to open the Run dialog box.
• Type outlook.exe /resetnavpane and pressEnter.

This will reset the navigation pane to its default settings.

Create a New Outlook Profile

There may be corruption in your current Outlook profile. You can try creating a new profile:

• Go to Control Panel > Mail.
• Click on Show Profiles.
• Select Add, then follow the prompts to create a new profile.
• Set this new profile as the default and restart Outlook.

Check for Conflicting Add-ins

Sometimes, an add-in can cause issues with Outlook starting. Since safe mode didn’t work, you might try manually disabling add-ins:

• Open Control Panel > Mail > Show Profiles > Manage Profiles > Add-ins.
• Uncheck any unnecessary add-ins and try to restart Outlook.

Repair Office Installation

If the problem persists, consider repairing your Office installation:

• Go to Control Panel > Programs and Features.
• Find Microsoft Office in the list, right-click on it, and select Change.
• Choose Quick Repair and, if needed, follow up with an Online Repair.

Check Exchange Server Connectivity

If you're using an Exchange account, the issue could be with the connection to the Exchange server. Verify with yourIT team or try switching your connection (e.g., switching from Wi-Fi to Ethernet) to see if that helps.

Run Microsoft Support and Recovery Assistant:

Download Microsoft Support and Recovery Assistant from Official Microsoft Download Center

Install Microsoft Support and Recovery Assistant from a network share or internet location - Microsoft 365 | Microsoft Learn

• Download and install the Microsoft Support and Recovery Assistant tool.
• This tool can help diagnose and fix issues with Outlook.

If these solutions do not resolve your issue, it may be necessary to consider more advanced troubleshooting options, such as checking for corrupt files or even reinstalling Office if all else fails.

I hope one of these steps helps you regain access to Outlook. Please let me know if you need further assistance or clarification on any of these steps!

Please understand that our initial response may not always resolve the issue immediately. However, with your help and more detailed information, we can work together to find a solution.

Appreciate your patience and understanding and thank you for your time and cooperation. Have a great day!

Sincerely,

Microsoft Community Moderator

"Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The attempt to log on to Microsoft Exchange has failed."

I tried all the steps below and I cannot open it in safe mode.

1. Start Outlook in safe mode: Start > Run > Type Outlook /safe > in the choose profile dialog, accept the default setting of Outlook and choose OK (if prompted, enter your password).
2. Repair Outlook Data Files.
3. Restart your PC and reopen your Outlook.

I just can't get Outlook to open.

Delete outlook folder from registry, that works for me, good luck...

"Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Profiles"

If you are having issue try running this in the Run window or cmd.

C:\PROGRA~2\MICROS~1\Office16\MLCFG32.CPL

or you can navigate to C:\Programs (x86)\Microsoft Office\Office16\MLCFG32.CPL

This will open up the mail setup

Our company has decided to use virtual machines. We don't have admin rights to these terminals. As a result easily solved Windows problems become nightmares while we wait for our over burdened IT department to respond. I have been using Outlook in one version or another since it's inception. I've never had a problem with it (at least a problem that I couldn't fix) but I am now at the mercy of my company's IT department. I usually use my laptop to connect but the company is poo pooing on the use of external devices on their pristine (read buggy) system. I'm trapped. There's no point to this post I'm just venting.

This is exactly my issue...
Everything works fine at the first startup, then something seems to be corrupted and it stops working...

Out of interest, what Antivirus did you install?

Hi

Our issue was that one of the mailboxes the user used, already had access to the mailbox via shared mailboxes. So the user logged in with User A, and User A had access to User B's mailbox. However, the user also logged in to Outlook with User B mailbox. I think that was our issue because we no longer have this problem, after not logging in with User B. It could also be an issue with User B's mailbox .ost file or whatever it could've been.

We use Eset Antivirus for reference :)