Gartner defines unified communications as a service (UCaaS) as a multitenant, subscription-based service that is cloud-delivered. It provides business telephony features; public switched telephone network (PSTN) connectivity that enables inbound and/or outbound external calling; and collaboration features, such as messaging and meetings. UCaaS services can be consumed by end users with traditional handsets, desktop clients, web clients, meeting room systems and mobile apps. UCaaS is used by organizations to securely communicate and collaborate — both internally and externally. It includes telephony, messaging and meetings. UCaaS providers may offer variations of each of the three core modes of communication and also offer a range of cloud contact center functionalities, either self-developed or through integration/partnerships with cloud contact center specialists. Gartner’s definition of meetings for the UCaaS market mostly focuses on the capabilities for internal collaboration, work from home and external presentation meeting use cases. Other specialized use cases — such as webinar, remote support, distance learning and training — are often available from UCaaS offerings, but are not mandatory for inclusion in this research. These use cases are part of a separate market defined by Gartner (the meeting solutions market).