You’re correct - at the moment, there’s no way to share a Custom GPT with access restricted only to a specific set of email addresses (“whitelisted email”).
Right now, OpenAI’s sharing options are limited to:
Private: Only you (the builder) can access it.
Shared by link: Anyone with the link can use it.
Published to the GPT Store (public): Discoverable by everyone.
There isn’t a built-in mechanism to require sign-in with a particular email or domain before use.
Workarounds you might consider
Client-only OpenAI account: Ask your client to create (or use) an OpenAI account, and then share the GPT privately by link with only them. While technically they could pass on the link, only logged-in accounts can access.
Custom wrapper: Instead of sharing the GPT directly, embed it behind your own authentication layer (e.g. a web app or portal where you control who can log in). The app would call the GPT API on the backend, and you’d whitelist the client’s email there.
Enterprise features: Some enterprise-level OpenAI solutions (like ChatGPT Enterprise or Team workspaces) offer more granular access controls, though not yet email whitelisting for Custom GPTs.