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Email Systems

Components:
-Messages (ASCII,MIME)
-Message Transfer Agent (SMTP, X.400): Used to send email
-Mailboxes:Used to store email
-Mailbox Access (POP3, IMAP4, HTTP): Used to retrieve email
-Mail Client (MS Outlook, Thunderbird)

Mail Message

Text Data Stream
Format: header and body.

Email Header

Contains addressing, routing, and format information

Email Body

Contains message itself

MIME

Multipurpose Internet Mail Extensions (MIME) was developed to allow binary data to be easily transferred within an email message.

SMTP

Simple Mail Transport Protocol
Used to deliver internet email. An SMTP server acts as a daemon, that is it listens for input.
-Listens on TCP port 25
Used to relay messages around the internet until the intended recipient is found.

Mail Relaying

Mail is relayed from one SMTP server to the next until the server that is responsible for local delivery is located.
-The DNS name space is used for locating mail servers

MX Record

used to declare the mail servers that are responsible for receiving inbound messages from the internet

POP3

Post Office Protocol
-Used to retrieve mail from a mailbox
-Listens on TCP port 110
-POP3 is an ASCII protocol
-Must have account and password
-Primarily used to retrieve messages from a mailbox for storage in a local message store.
-Once the message is downloaded the message is deleted from the server.

IMAP

-Latest version is IMAP4
-On port 143 or 220
-Can view just the header and then download what you want
-Can display and use multiple folders on the server
-Primarily used when you want mail to remain on server.

SPAM

Unsolicited Commercial email

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