Credentials cannot be used for NTLM error while configuring NTLM proxy authentication in Docker

Issue

When a Mendix application is deployed on-premise in a Docker container and the network requires NT LAN Manager (NTLM) authentication through a proxy to reach an external endpoint, the following error occurs:

Credentials cannot be used for NTLM.

Mendix does not natively support NTLM proxy authentication, so outbound API calls through the proxy fail to authenticate successfully.

Environment

Applications hosted in On-Premises

Cause

The Java Virtual Machine (JVM) does not attempt NTLM negotiation by default when routing traffic through a proxy. Since Mendix does not natively support NTLM proxy authentication, the authentication handshake fails when the proxy enforces NTLM.

Solution/Workaround

To properly support NTLM authentication, implementing a custom Java action to handle NTLM authentication for the proxy connection is necessary.

Implementation assistance for custom Java actions is outside the scope of Support. The following options are available for assistance:

• Post questions on the Mendix Community forum for community support
• Contact your Customer Success Manager to connect with the Expert Services team for paid consultancy services
• Engage a Mendix partner for tailored solution development

Additional information

Not applicable