What is a Mail Server?

Mail server is ,

Is the computerized equivalent of your friendly neighborhood mailman
Every email that is sent passes through a series of mail servers along its way to its intended recipient
Although it may seem like a message is sent instantly – zipping from one PC to another in the blink of an eye – the reality is that a complex series of transfers takes place
Without this series of mail servers, you would only be able to send emails to people whose email address domains matched your own – i.e., you could only send messages from one example.com account to another example.com account