SMTP is short for Simple Mail Transfer Protocol. If you append "server" to SMTP you get an SMPT Server which is an email-based server that allows you, applications, or other users to send and receive emails between two parties. Gmail, Outlook, Yahoo, etc... are SMTP servers. When you signup for an email account at these services, you get an ID that is capable of sending and receiving emails on that specific SMTP Server.
By default, an SMTP server will have an address that will be consumed by other mail clients like MailKit that we will be using for this article. For this, to work we have to obtain SMTP server details like Host, Port, Security Settings, Username/Password, etc...