Hopefully I seem to have solved the issue by:- Uninstalling Office suite
- Reinstalling Office Suite
- Set a new profile
I've tested by closing down and restarting the laptop multiple times (which was the problem last time) and it still seems to work OK
Outlook 2021 Classic (Not 365) WiIl Not Open - but forum removes my answers advising due to Code of Conduct
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Keith Morgan
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My answers keep getting deleted advising as breaking Code of Conduct but do not understand why as nothing offensive in messages.
I've edited my question as below (removing case numbers and phone numbers) in the hope that this gets through.
Previous MS support has tried resetting new Outlook profile but did not work.
The last MS Support person to contact me21Nov25 from California quoted a new case number, but then advised that he could not assist and referred me to MS Commercial Support Team on two UK numbers, which are meant to provide 24hr support. However, on both numbers the auto voice does not recognise the case number of refers me to 365 support which is incorrect. The UK numbers then referred me to aka.msflashprosupport, but this then bounced me to JustAnswer who wanted me to pay to assist. JustAnswer then also provided a different number for MS UK Business Support Line – but this doesn’t work!
Still desperate to speak to someone in the MS UK Business Support who can help solve this issue.
Hornblower409 responded:
“For the problem where your answers and comments get deleted, please post a new Question in the Community Forum so the Mods can investigate. (Include a link to this question)
Outlook | Windows | Classic Outlook for Windows | For home
Answer recommended by moderator
Answer recommended by moderator
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Keith Morgan 0 Reputation points
2025-11-24T07:43:09.1133333+00:00
3 additional answers
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Austin-H 8,350 Reputation points Microsoft External Staff Moderator2025-11-22T15:25:45.5966667+00:00 Hello @Keith Morgan
Thank you for posting question to Microsoft Q&A Forum.
As far as I know, the Business support is included in Microsoft 365 package.Please check on this link: https://support.microsoft.com/en-us/office/microsoft-365-customer-service-and-support-96162163-b3aa-498b-bbbb-5e757b0f31da
It might be difficult to find the callback support if you have technical issue with Outlook 2021 (which belongs to Office 2021). My apology for any conveniences caused by this issue - as this forum is peer-to-peer support so I could not check the ticket system to provide you an answer about your ticket question.
Regarding Outlook 2021 issue, may I know if you have had this issue when opening Outlook 2021 like this screenshot?
Did you recall on the part MS Support Team tried to reset Outlook profile ? Was it related to second part in Q&A Assist's answer?
If it does not work, please search for the app "Get Help" in your computer, then type "Cannot open Microsoft Outlook" and select the PC > Office 2021 > proceed with troubleshooting steps there.
I hope this could possibly help while you are waiting for answers about the ticket at the moment. If you have more questions/update about Outlook, please feel free to ask here.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.
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Austin-H 8,350 Reputation points Microsoft External Staff Moderator
2025-11-22T15:29:27.6433333+00:00 Hello @Keith Morgan
Thanks for your recent update. I was composing my own answer also at the same time when you provided information.Were you able to run Windows + R > type "outlook /safe" ? Or it still returned the same error?
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Keith Morgan 0 Reputation points
2025-11-22T15:52:58.7233333+00:00 Thanks Austin
Unfortunately when I try to run Outlook.exe /safe it still comes up with the same error message "Cannot start MS Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The attempt to log on to MS Exchange has failed"
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Keith Morgan 0 Reputation points
2025-11-22T15:54:13.1666667+00:00 Austin
Also I am not using MS365.
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Austin-H 8,350 Reputation points Microsoft External Staff Moderator
2025-11-22T16:20:33.1066667+00:00 Hi @Keith Morgan
Thank you for your response.Did you try these options? If you haven't done these steps before, consider these suggestions:
1.Press Windows key + R, type outlook.exe /resetnavpane, then select OK. This clears corrupted pane customizations that can block startup.
2.Go to Control Panel → Programs and Features → Microsoft Office → Change → Online Repair. This replaces broken binaries and fixes common startup crashes. -
Keith Morgan 0 Reputation points
2025-11-22T16:43:35.1033333+00:00 Thanks Austin
But when I action Windows key + R, type outlook.exe /resetnavpane I just get the same error message "Cannot start MS Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The attempt to log on to MS Exchange has failed".
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Austin-H 8,350 Reputation points Microsoft External Staff Moderator
2025-11-22T17:04:34.51+00:00 Hello Keith Morgan
Thanks for your response.Please consider trying this step and make sure that your emails are on cloud already.
Open File Explorer and look for this directory: C:\Users[yourusername]\AppData\Local\Microsoft\Outlook
Look for file OST (ends at *.ost) then you could create an example folder named "Old", then try to move all *.ost files into the "Old" folder you just created.
After that, you could try to re-open Outlook.
This step is recommended if the Outlook profile data files are corrupted. If this could not fix the issue, I am thinking of Outlook reinstallation - and if this option does not fix the issue, I am thinking of going with new Windows profile (This is also considered as the worst scenario).
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Austin-H 8,350 Reputation points Microsoft External Staff Moderator
2025-11-24T01:40:33.6533333+00:00 Hello Keith Morgan
I hope this comment finds you well.May I know if you have tried my suggestions above?
I am looking forward to your update.
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simo-k 79,110 Reputation points Volunteer Moderator2025-11-22T17:09:48.8366667+00:00 What is your email connection type? (Exchange, IMAP, or POP)
If you are using an Exchange connection, please try deleting the OST file.
If you are using a POP connection, are you storing the PST file you use under OneDrive management?<Japanese>
メールの接続方式は何ですか？ （Exchange接続、IMAP接続、POP接続）
Exchange接続の場合は、OSTファイルを削除してみてください。
POP接続の場合は、利用しているPSTファイルをOneDrive管理下に保存していませんか？-
Keith Morgan 0 Reputation points
2025-11-22T17:38:38.14+00:00 Simo
I am using an Exchange server with Ionos.
This is Windows 11 Office 2021 (not MS 365)
Currently I can only access my emails via https://exchange.ionos.eu/ or via my iPhone.
How do I delete the OST file? And do I need to have backed up emails, calendar and contacts prior?
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Q&A Assist2025-11-22T14:05:21.6466667+00:00 AI generated content. This question contains an answer created with AI from Q&A Assist. Learn moreIt seems you are experiencing issues with Outlook 2021 Classic not opening, and you're also facing challenges with your posts being removed from the forum due to the Code of Conduct. Here are a few suggestions to address your Outlook issue:
- Check for Updates: Ensure that your Outlook 2021 is updated to the latest version. Sometimes, issues can arise from outdated software.
- Create a New Profile: Since resetting the profile did not work previously, you might want to try creating a new Outlook profile again. Here’s how:
- Open Control Panel and click on Mail.
- Click Show Profiles.
- Select the existing profile and click Remove (make sure to back up any important data).
- Click Add to create a new profile, enter a name, and follow the prompts to set it up.
- Run the Classic Outlook Advanced Diagnostics Troubleshooter: This tool can help identify and fix issues related to Outlook. Make sure you are using the same Windows device that has Outlook installed.
- Repair Office: You can try repairing your Office installation. Go to Control Panel > Programs > Programs and Features, select Microsoft Office, and then click on Change. Choose the repair option and follow the instructions.
- Check for Conflicts: Ensure that no other programs or add-ins are conflicting with Outlook. You can start Outlook in safe mode to see if it opens without any add-ins. To do this, hold down the
Ctrlkey while starting Outlook.
If these steps do not resolve the issue, consider reaching out to Microsoft Support directly through their official channels for further assistance.
Regarding your posts being removed, it might be helpful to review the Microsoft Q&A Code of Conduct to ensure that your contributions align with their guidelines. If you believe your posts are being incorrectly flagged, you can follow the advice given in the forum to escalate the matter.
References:
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Keith Morgan 0 Reputation points
2025-11-22T15:20:56.83+00:00 Thanks have tried everything above without success as:
1: Updates I believe my Outlook 2021 is the latest available update.
2: Create New Profile MS support has already tried this when controlling my laptop but this also failed.
3: Classic Outlook Advanced Diagnostics Troubleshooter Ran SarA for “Microsoft Outlook won’t start” but result “Generic failure An issue occurred while running the Classic Outlook Connectivity troubleshooter. Please use Get Help to search for a new solution”. Then Ran in SarA: “Classic Outlook Advanced diagnostics troubleshooter”, but this states “To gather the most pertinent information, please make sure that Microsoft Outlook is actively running”, but obviously cannot open Outlook! Just get a black screen pop up and close.
4: Repair Office
Tried ‘Quick Repair’ and despite message stating ‘done repairing’ still get the same error message "Cannot start MS Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The attempt to log on to MS Exchange has failed"So then tried ‘Online Repair’ but after this completing and stating “You’re all set” still get the error message "Cannot start MS Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The attempt to log on to MS Exchange has failed"
5: Check for Conflicts/ Safe Mode Tried opening Outlook in SafeMode but still get the same error message "Cannot start MS Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The attempt to log on to MS Exchange has failed".
So despite your recommendation “If these steps do not resolve the issue, consider reaching out to Microsoft Support directly through their official channels for further assistance”, I would be delighted to be able to talk to a real person from Microsoft Support / MS UK Business Support Line, but to date after having contact with at least 5 different MS support people to date I’ve been referred to different areas of support that unfortunately have proved to be dead ends.
Q: Microsoft Support / MS UK Business Support Line – are you out there?
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