GSA has negotiated powerful email as a service (EaaS) discounts for all federal agencies. These cloud-based services support agency missions at all levels, including smart phones. GSA adds that "You can buy Email as a Service (billed per mailbox), Office Automation, Electronic Records Management, Migration Services, and Integration Services, with security requirements at the FISMA moderate-impact level (and FISMA high-impact level for the Secret Enclave delivery model). The delivery models are Government community cloud, Private cloud, Secret enclave cloud, and Public cloud. Details here: