After you configure federated SAML single sign-on (SSO) with Broadcom Login for Email Security.cloud, you are getting 400 Bad Request Error code: General_NonSuccess.
Email Security.cloud
The error is caused by the incorrect attributes the customer's IdP sends during the authentication process.
When you configure federated SSO through Broadcom Login, the support gives the Audience and ACS URLs to complete the SSO configuration on IdP side. The URLs themselves are correct and valid, but you need to ensure the attributes are correct (Attribute mapping). The validation is recommended to be carried out with the customer’s IdP support.
As a way of diagnosing the issue, it's possible to see which attributes are sent, for this its required to capture a HAR file or SAML traces of the session/steps taken up until the error page. Clear the cache on all the involved URLs before starting the process.