What does this "AuthenticationFailedSasError " error mean?

Question

What does this "AuthenticationFailedSasError " error mean?

Alvin Ung 25

What exactly does this "AuthenticationFailedSasError" error mean when there is a failed login attempt to a mailbox on Exchange Online?

Jame Xu-MSFT 4,201 Reputation points

2023-02-16T02:45:56.9833333+00:00

Hi @Alvin Ung ,

Could you provide specific information about the error reported? Based on the errors you provided, I found a document that you could refer to: Azure AD Authentication and authorization error codes

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Jame Xu-MSFT 4,201 Reputation points

2023-02-16T02:45:56.9833333+00:00

Hi @Alvin Ung ,

Could you provide specific information about the error reported? Based on the errors you provided, I found a document that you could refer to: Azure AD Authentication and authorization error codes

Answer 1

Givary-MSFT 35,786 Microsoft Employee Moderator

@Alvin Ung Apologies for the delay in reviewing this post, the "AuthenticationFailedSasError" error is with regards to MFA (Multi-Factor Authentication) typically indicates that there was a problem with the authentication process while using a SAS (Strong authentication service ) token that requires MFA. above screenshot just states user login failed because of mfa, however we need to review audit/sign in logs of Azure AD for further information why MFA failed, what is the specific error code is mentioned in the logs.

Let me know if you have any further questions, feel free to post back.

Alvin Ung 25 Reputation points

2023-02-21T20:39:21.18+00:00

Hi @Givary-MSFT ,

Thank you for your response! The information you provided is sufficient for what I was looking for, and gave me a better understanding of what this login error really means. Thank you!
Xavier Gonzalez 0 Reputation points

2026-03-20T02:52:11.5866667+00:00

67 tutorials 67

Answer 2

Alvin Ung 25

Hi Jame,

Thank you for the documentation. I do not see this specific error on there though.

Here are some additional details regarding this event:

Operation   | UserLoginFailed
RequestType | SAS:EndAuth
LogonError  | AuthenticationFailedSasError
Workload    | AzureActiveDirectory
UserAgent   | Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/109.0.0.0 Safari/537.36

Xavier Gonzalez 0 Reputation points

2026-03-20T02:51:30.07+00:00

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Answer 3

Xavier Gonzalez 0

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What does this "AuthenticationFailedSasError " error mean?

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