Licence management & emailing server API/CMS for desktop app

We need a back-end web API and CMS site for our desktop software, which will manage the entry, validation and management of licences; as well as providing an email service for the software. The CMS will need to provide a way to enter and manage licence information with specific fields, and delete or deactivate licences. The API will need to provide a way that our software can automatically verify its licence information, linking a licence to a single installation via a unique device ID. The process and specifications for doing this are already devised, and so a generic system, such as Auto PHP Licencer will not suffice. We will provide the key code snippets that format, validate and verify licences. The web service should also provide an API that our software can use to send emails. This will simply need to support HTML content and file attachments. Naturally, this system will need to be secure. Therefore admin account management is required for the web interface. The software API will need to use some form or authentication or authorization. Suggestions for the most appropriate solution are welcome, and will need to be confirmed with the development team. cURL is the preferred method of communicating with the server. The system will run on our dedicated server hosted with UK2, and PHP is our preferred language/platform. Technical details will need to be discussed and confirmed.