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Aquiring Token from ACS has failed.

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Posted on by DP-06061321-0

Morning,
I wanted to change the configuration of Dynamcis 365 On-prem to communicate with Exchange Online after adding a certificate and assigning the application itself mail server profile(connection test) sees exchange that is link:https://outlook.office365.com/EWS/Exchange.asmx It also sees the user but at the authentication of the mailbox has this error:
Aquiring Token from ACS has failed.
I tried to do the instructions from this link:
https://community.dynamics.com/forums/thread/details/?threadid=2fabeeca-181d-f011-998a-7c1e52189d0f
However, some commands do not work, that is, when running the Set-CrmRecord command there is no such aprameter as -AttributeList. I would ask you to update the intructions or help me to consider the problem.
Thank you for your help.

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Holly Huffman 6,538 Super User 2025 Season 2 on at

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Good morning, afternoon, or evening—depending on where you are in the world!
Hope you're doing well.

Thanks for the detailed context. You're encountering the error "Acquiring Token from ACS has failed" while configuring Dynamics 365 On-Premises to connect with Exchange Online. This is a known issue that can stem from several misconfigurations or outdated guidance.
Here’s a breakdown of what’s going on and how to resolve it:

Root Cause
The error typically occurs during the OAuth authentication handshake between Dynamics 365 On-Prem and Exchange Online. It often points to issues with:

Incorrect or expired certificates

Misconfigured application registration

Outdated PowerShell commands or parameters

Missing or misused claims-based authentication setup

Resolution Steps

Use Updated Microsoft Documentation
Refer to the official Microsoft guide for setting up server-based authentication between Dynamics 365 On-Prem and Exchange Online: Connect Exchange Online to Dynamics 365 On-Premises

Avoid Deprecated Commands
The Set-CrmRecord -AttributeList command mentioned in the community thread you referenced is outdated or incorrect. Instead, use Set-CrmRecord with the -Fields parameter or switch to Set-CrmEntity if you're using XrmTooling.

Validate Certificate Configuration
Ensure the certificate used for the application is:

Trusted by the Dynamics server

Not expired

Properly assigned in the application registration in Azure AD

Check ACS Trust Settings
If you're still using ACS (Access Control Service), consider migrating to Azure AD-based authentication, as ACS is deprecated and may not be supported in newer configurations.

PowerShell Compatibility
If you're using PowerShell 7+, note that some modules (like MSOnline or ExchangeOnlineManagement) may not be fully compatible. Try using PowerShell 5.1 for setup tasks.

Next Steps

Revisit your PowerShell scripts and replace deprecated parameters.

Follow the Microsoft documentation step-by-step, especially around certificate and app registration setup.

Note: I collaborated with AI to help craft this response and ensure it’s as accurate and helpful as possible.
Hope this helps some!

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DP-06061321-0 26 on at

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What certificate should be added, should it be the server certificate(domain certificate),SSL certificate, or some other certificate we should add?

After configuring the application and performing the connection test, the second control appeared in green, as shown in the photo below.

All the commands from https://learn.microsoft.com/en-us/dynamics365/customerengagement/on-premises/admin/connect-dynamics-365-on-premises-exchange-online?view=op-9-1 have been executed and entries in the Database have been added.

We do not have Claims-Based Authentication configured-nowhere in the manual was it spelled out that this must be done. We also do not have ADFS which is required to configure this option.

Check ACS Trust Settings- How to force Other authorization? When configuring the Mail Profile Server, there is no option to select other authorization than ACS. How can we change this?

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DAnny3211 11,397 on at

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Hi,

Thanks for sharing the issue! The error "Acquiring Token from ACS has failed" typically indicates a problem with authentication between Dynamics 365 On-Premises and Exchange Online, especially when using server-side synchronization.

Here are a few steps to help troubleshoot and resolve the issue:

Verify Certificate Setup:

Ensure the certificate used for OAuth is correctly installed and trusted by both Dynamics 365 and Exchange Online.

The certificate must be registered in Azure AD and linked to the application.

Check Application Registration:

Confirm that the App ID and Redirect URI are correctly configured in Azure AD.

The app must have the necessary API permissions for Exchange (e.g., full_access_as_app).

Update PowerShell Commands:

The Set-CrmRecord command may have changed or been deprecated. Instead, use the latest version of the Dynamics 365 PowerShell module.

You can try using Set-CrmSetting or New-CrmSetting depending on your version.

Use Updated Instructions:

The link you referenced may be outdated. I recommend checking the official Microsoft documentation for OAuth configuration for server-side sync: Configure OAuth for server-side sync

Test Mailbox Configuration:

After setup, go to Mailboxes in Dynamics 365 and run the Test & Enable Mailbox function to verify connectivity.

If the issue persists, consider opening a support ticket with Microsoft to get help tailored to your environment and version.

Hope this helps!
Please mark this response as helpful if it answered your question.

Best regards!

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