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[Access Control] Troubleshooting Connection Issues to Microsoft 365 in Outlook

Question

In an Access Control environment, I am unable to connect to Microsoft 365 using Outlook.
Please advise on how to resolve this issue.

Answer

Please follow the troubleshooting steps below.
The order in which you should perform the steps depends on the scope of the issue.

  • If the issue occurs for All Users: Please try the troubleshooting steps in the following order: 0. → 1. → 2. → 3. → 4. → 5.
  • If the issue occurs for some users: Please try the troubleshooting steps in the following order: 0. → 5. → 4. → 3. → 2. → 1.

Step 0. Check for Microsoft 365 / HENNGE One service incidents+

HENNGE One Status Dashboard
How to check Microsoft 365 service health

Step 1. [If this occurs on first use or after DNS changes] Check DNS settings+

Please verify that the DNS records for the domain of the user attempting to connect, such as autodiscover, are correctly registered.
If you have separate DNS servers for internal and external use, please ensure that Both servers have the correct values registered.
<Reference Article>
"Create DNS records for Microsoft 365 using a Windows-based DNS" (external link)
"How to use Remote Connectivity Analyzer to troubleshoot single sign-on (SSO) issues in Microsoft 365" (external link)

Step 2. Check URL filtering+

If you are using a URL filtering service, please ensure that communication to Access Control is allowed.

Step 3. Check connection using a newly created user+

Please verify that you can connect using a newly created user.
If you cannot connect with existing users but can connect without issue using a newly created user, there may be a problem with internal parameters held by Access Control.
Please contact HENNGE One Technical Support.

Step 4. Check if Access Control access permission conditions are met+

If you are using Outlook 2016 and Exchange Online is configured to support WS-Trust authentication, please check whether the authentication request communication is reaching Access Control with your network's global IP address information.
[Access Control] Check access logs for All Users
Reference: "Microsoft 365 URLs and IP address ranges" (external link)

Step 5. Check Outlook / Windows OS settings+

If you are using Outlook 2013 / 2016, please try the following troubleshooting steps in order.

[Troubleshooting Steps]

  1. Disable Outlook add-ins
    You can determine if add-ins are causing the issue by starting Outlook in Safe Mode.
    Disable add-ins one by one and check if the issue is resolved.
    For instructions on disabling add-ins, please refer to the following:
    Disable add-ins in Outlook for Windows (external link)
  2. Delete credentials
    1. Click [Start] - [Control Panel].
    2. Click [User Accounts] - [Credential Manager].
    3. Click the relevant credential to expand it.
    4. Click [Remove from vault] and delete All credentials containing the following keywords:
    - Credentials containing the keyword [outlook]
    - Credentials containing the keyword [office365]
    - Credentials containing the keyword [onmicrosoft.com]
    - Credentials containing the keyword [MicrosoftOffice1x ~ SSPI]
    - Credentials containing the keyword [ADAL]
    - Credentials containing the keyword [Autodiscover]
  3. Recreate Outlook profile, including deleting OST files
  4. Reinstall the Outlook app
  5. Use the Recovery Assistant tool
    About Microsoft Support and Recovery Assistant (external link)