Which method allows NetSuite to authenticate using third-party service providers?

The method that enables NetSuite to authenticate using third-party service providers is Inbound Single Sign-On (SSO). Inbound SSO facilitates a seamless login experience by allowing users to leverage external authentication sources, such as identity providers, to access NetSuite without needing a separate NetSuite password. This streamlines user management and enhances security by centralizing authentication through a trusted third party.

When employing Inbound SSO, organizations can use methods such as SAML (Security Assertion Markup Language) or OAuth as part of the integration with their existing identity solutions, which improves user experience and administration. The integration reduces the risk associated with managing multiple credentials while aligning with modern security practices.

Other options like Two-factor Authentication focus on adding an extra layer of security to login processes but do not specifically relate to third-party authentication services. Custom User Roles deal with permission and access configurations within NetSuite rather than authentication. External Password Management involves managing passwords outside of NetSuite but does not directly facilitate authentication via third-party identity providers. Thus, Inbound SSO is the most appropriate and effective method for authenticating users through third-party service providers.