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→Learning About the Services Involved in an Email Delivery
In the diagram displayed above, the elements include:
* A '''User Account''' - i.e. the The individual who wants to send or receive mail messages.* An '''MUA''' (email client). This is the application that the individual uses to send or receive mail messages. It can be a '''native application''' or a '''web application'''. You will learn how to setup and use both types of these applications throughout the remainder of this course.* Two '''MTAsMTA'''servers. These are the servers responsible for getting your emails to the <u>destination</u> server.
** They are similar to routers (which route packets) but work on the <u>application</u> layer rather than the <u>network</u> layer.
** In our example, there are only two MTAs - but there can be several.
** You connect to your MTA over a <u>secure</u> connection, so your emails can't be read by the operators of the network you're connected to.
** The mail message then travels the rest of the way to the destination MTA <u>unencrypted</u>, so anyone with access to the routers in-between can read all your emails. That is why many organizations will refuse to send you confidential information over email.
* The '''LDA/MDA''' Server. This server will receive the email from the MTA, and will store it on disk in some format. '''MailDir''' and '''MBOX''' are the most popular mailbox formats.
* '''IMAP/POP3''' server(s). When sending an email, you send it to the destination using your MTA, but you also want to save it in your '''"Sent"''' folder for yourself. This is accomplished by a separate connection to either your '''IMAP''' or '''POP3''' server.
** Thus, a situation can occur that although you sent your email successfully, it may never make it to your "Sent" folder - the <u>second</u> connection to your IMAP server is quite unrelated to the first connection to the '''SMTP''' server.
