A customer approached us with a need to allow access to a private Mailsac domain without requiring authentication from his students who may not have an email address.
We published a Nextjs application (GitHub - mailsac/mailsac-self-hosted-ui) that allows customers to run their own Mailsac user interface. This user interface relies on API calls to Mailsac to grant read only access to email that the API key has access to.
Full details on how to run and configure the application locally or on vercel are available in the repos README or on our blog.