OAuth token requests from server consistently return HTTP 404 at the ESTS gateway layer.

Question

OAuth token requests from server consistently return HTTP 404 at the ESTS gateway layer.

Anthony Bluthner 5

Firstly, I have already worked with four different support agents across multiple platforms, including Plesk, Fasthosts, and Microsoft 365.

Microsoft 365 Support directed me to Azure Technical Support, which resulted in a $29 charge to be referred to Microsoft Q&A.

All relevant troubleshooting, configuration reviews, and validation checks have already been completed.

I have removed the server IP address from this post for privacy reasons and can provide it directly to the assigned Microsoft engineer if required.

Below is the latest assessment from Microsoft 365 Support:

OAuth token requests from my server consistently return an HTTP 404 response instead of the expected JSON payload. This behavior occurs across multiple authentication flows and affects both personal and business Microsoft accounts.

Plesk has confirmed they cannot reproduce the issue in their environment, indicating the problem is specific to the originating server, network path, or IP address.

Key Findings

Response headers show:

x-ms-gateway-slice=estsfd is present.

x-ms-ests-server is missing.

x-ms-request-id is missing.

This suggests the request reaches the Microsoft ESTS (Entra ID) gateway but does not proceed to the authentication backend.

Assessment

The issue does not appear to be related to application code, configuration, or the Plesk extension. Based on the behavior observed, possible causes include:

IP reputation-based filtering

Gateway or front-door filtering

Routing or region-specific service issues

The issue is consistently reproducible from this server, affects different authentication methods, and cannot be reproduced from other IP addresses.

Request

Could the Microsoft Entra ID team please investigate whether the originating IP address or associated network is being affected by gateway filtering, reputation-based mitigation, routing anomalies, or any other service-side restriction that may prevent requests from reaching the authentication backend?

Sridevi Machavarapu 33,820 Reputation points Microsoft External Staff Moderator

2026-06-15T11:03:01.7766667+00:00

Hello Anthony Bluthner,

We need few details to proceed further. Please check your Private messages tab and provide those details.
Saravana Kumar D 170 Reputation points Microsoft External Staff Moderator

2026-07-29T12:34:31.3133333+00:00

Hello @Anthony Bluthner

Based on the behavior observed, the issue may occur because the OAuth request is not being fully processed after reaching the ESTS gateway layer. Since the issue is consistently reproducible from a specific server and cannot be reproduced from other IP addresses, possible contributing factors include network path inconsistencies, routing issues, gateway-level filtering, IP reputation restrictions, or environment-specific connectivity conditions. The absence of the expected authentication service headers suggests that the request may not be reaching the backend authentication service for processing.

Thank you
Saravana Kumar D 170 Reputation points Microsoft External Staff Moderator

2026-08-04T10:23:12.0166667+00:00

Hello @Anthony Bluthner

Greetings!

Please let me know whether suggestion provided above was helpful or not for the further troubleshooting.

Thank you

Your answer

Sridevi Machavarapu 33,820 Reputation points Microsoft External Staff Moderator

2026-06-15T11:03:01.7766667+00:00

Hello Anthony Bluthner,

We need few details to proceed further. Please check your Private messages tab and provide those details.
Saravana Kumar D 170 Reputation points Microsoft External Staff Moderator

2026-07-29T12:34:31.3133333+00:00

Hello @Anthony Bluthner

Based on the behavior observed, the issue may occur because the OAuth request is not being fully processed after reaching the ESTS gateway layer. Since the issue is consistently reproducible from a specific server and cannot be reproduced from other IP addresses, possible contributing factors include network path inconsistencies, routing issues, gateway-level filtering, IP reputation restrictions, or environment-specific connectivity conditions. The absence of the expected authentication service headers suggests that the request may not be reaching the backend authentication service for processing.

Thank you
Saravana Kumar D 170 Reputation points Microsoft External Staff Moderator

2026-08-04T10:23:12.0166667+00:00

Hello @Anthony Bluthner

Greetings!

Please let me know whether suggestion provided above was helpful or not for the further troubleshooting.

Thank you