In the early 90’s, the Turing test, which allows determining the possibility of thinking by computers, was developed. It consists in the following. A person talks to both the person and the computer. The goal is to find out who his interlocutor is — a person or a machine. This test is carried out in our days and many conversational programs have coped with it successfully.
At a high level, a conversational bot can be divided into the bot functionality (the "brain") and a set of surrounding requirements (the "body"). The brain includes the domain-aware components, including the bot logic and ML capabilities. Other components are domain agnostic and address non-functional requirements such as CI/CD, quality assurance, and security.

Authentication. Users start by authenticating themselves using whatever mechanism is provided by their channel of communication with the bot. The bot framework supports many communication channels, including Cortana, Microsoft Teams, Facebook Messenger, Kik, and Slack. For a list of channels, see Connect a bot to channels. When you create a bot with Azure Bot Service, the Web Chat channel is automatically configured. This channel allows users to interact with your bot directly in a web page. You can also connect the bot to a custom app by using the Direct Line channel. The user's identity is used to provide role-based access control, as well as to serve personalized content.
Not integrated. This goes hand-in-hand with the contextual knowledge, but chatbots often suffer from “death by data silo” where their access to data is limited. If a chatbot is “chatting with” a customer, they not only need to access the contextual data of their customer but also have access to every place where the answer to the customer’s question may reside. Product documentation site, customer community, different websites are all places where that answer can be.

As the above chart (source) illustrates, email click-rate has been steadily declining. Whilst open rates seem to be increasing - largely driven by mobile - the actual engagement from email is nosediving. Not only that, but it's becoming more and more difficult to even reach someone's email inbox; Google's move to separate out promotional emails into their 'promotions' tab and increasing problems of email deliverability have been top reasons behind this.
A chatbot (also known as a spy, conversational bot, chatterbot, interactive agent, conversational interface, Conversational AI, talkbot or artificial spy entity) is a computer program or an artificial intelligence which conducts a conversation via auditory or textual methods.[1] Such programs are often designed to convincingly simulate how a human would behave as a conversational partner, thereby passing the Turing test. Chatbots are typically used in dialog systems for various practical purposes including customer service or information acquisition. Some chatbots use sophisticated natural language processing systems, but many simpler ones scan for keywords within the input, then pull a reply with the most matching keywords, or the most similar wording pattern, from a database.