Software as a Service (SaaS) - Provides access to software applications over the internet on a subscription basis, eliminating the need for installations and maintenance.

Platform as a Service (PaaS) - Offers a platform allowing customers to develop, run, and manage applications without the complexity of building and maintaining the infrastructure.

Infrastructure as a Service (IaaS) - Provides virtualized computing resources over the internet, requiring the user to manage the operating systems, storage, and deployed applications.

None of the above - The business should consider on-premises solutions for better control over their email services.