Getting email to work properly involves several different components. Each of these components must do a particular job and then hand off the email being delivered to the next component in the chain.
Sometimes a single server or application handles multiple components. Even when this is the case, troubleshooting is more effective when you continue to think of the system in terms of components. We look at each component in turn.
The Mail User Agent, or MUA for short, is the technical term for an email client. You use your MUA to send and receive email. Many things can do the job of the MUA such as a dedicated program, a web page, a smartphone, or even an application that sends out alerts.
The MUA’s job is to capture ...