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2440: 141 Web Site Administration Email Services Instructor: Enoch E. Damson.

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Presentation on theme: "2440: 141 Web Site Administration Email Services Instructor: Enoch E. Damson."— Presentation transcript:

1 2440: 141 Web Site Administration Email Services Instructor: Enoch E. Damson

2 The E-mail Environment E-mail evolved from a variety of proprietary systems In the 1980s and 1990s, people often had e-mail addresses on a number of systems The standard for current e-mail services is to use DNS with a special Mail Exchange record The Mail Exchange record contains the IP address of the mail server for a domain To allow users to send images, video, audio, and other binary files via e-mails, the Multipurpose Internet Mail Extension (MIME) specification was developed Email Services 2

3 The E-mail Environment… Protocols used by Email systems to communicate include: For sending mail: Simple Mail Transfer Protocol (SMTP) For retrieving email from electronic mailboxes Post Office Protocol (POP) Internet Mail Access Protocol (IMAP) Common e-mail packages (servers) include: Sendmail, Postfix (Linux) Microsoft Exchange (Windows) Email Services 3

4 Role of DNS in E-mail Systems A domain name, such as, needs to be associated with two IP addresses One IP address can be for a Web site Another IP address is for e-mail To associate a domain name, or any other host name, with the IP address of an e-mail server, you need a Mail Exchange (MX) record Email Services 4

5 E-Mail Providers Every email provider supplies three fundamental services: Send email Receive email Store received email at least temporarily Difference between email providers and their cost depends on: Versatility Security Extent of services Email Services5

6 E-Mail Services E-Mail services have three distinct components: Mail User Agent (MUA) – the mail client the user interacts with E.g. Kmail, Alphine, Elm (Windows, Linux) Mail Transfer Agent (MTA) – handles the process of getting mail from one site to another E.g. Sendmail, Postfix (Linux) Microsoft Exchange (Windows) Mail Delivery Agent (MDA) – takes the message and gets it to the appropriate user mailbox, when received at the site E.g. Procmail, Microsoft Exchange Email Services6

7 E-mail Protocols The core email protocols include: SMTP (Simple Mail Transfer Protocol) – used by MTAs to transfers e-mails from one server to another POP (Post Officer Protocol) – used by MDAs to deliver mail to users IMAP (Internet Message Access Protocol) – also used by MDAs to deliver mail to users MAPI (Messaging Application Programming Interface) – used with MS Outlook in conjunction with MS Exchange Server mail server HTTP – for WebMail accounts Email Services 7

8 Simple Mail Transfer Protocol (SMTP) The main standard for mail transport across the Internet Defines the method of sending mail from a host to another Its major strengths include its: Simplicity Platform-independent Requires that a host be capable of sending ASCII text to another host Typically done using port 25 (SMTP) on a mail server E.g. telnet mailserver 25 Email Services8

9 Common SMTP Commands Some major SMTP commands include: HELO – used by clients to introduce themselves to the server (originating hostname) E.g. HELO VRFY– verifies the email user DATA – specifies the body of the message QUIT – ends the SMTP session Email Services9

10 Common SMTP Headers Major SMTP headers include: MAIL FROM: – informs the mail server about the email’s origin (sender’s email address) E.g. MAIL FROM: RCPT TO: – specifies the receiver’s email address E.g. RCPT TO: RECEIVED: – identifies the email server that processed the message DATE: – indicates the date of the email SUBJECT: – shows the subject of the email message TO: – shows the recipient of the email message CC: – sends copies of the message to a list of email addresses Email Services10

11 Sample SMTP Session HELO WKS1 250 Hello [] MAIL FROM: 250 2.1.0 OK RCPT TO: 250 2.1.5 DATA 354 Start mail input; end with. This is a simple message. QUIT Email Services11

12 Installing and Administering Microsoft Exchange The Microsoft Exchange Server can be much more than a simple e-mail server It supports: SMTP, POP, and IMAP protocols Also supports the Lightweight Directory Access Protocol (LDAP) Collaboration in the form of chat services and instant messaging Interaction with other e-mail servers such as Lotus Notes, Novell Groupwise, etc Email Services12

13 Microsoft Exchange Features The Microsoft Exchange Server also has the following features: Unified messaging platform services Supports Voice Profile for Internet Mail (VPIM) – for interoperability between voicemail systems Conferencing services The conferencing server provides high performance through the Telephony API – a programming interface for efficient multicasting Chat services Includes a chat service based on the Internet Relay Chat (IRC) protocol Instant Messaging Newsgroups Requires the Network News Transport Protocol (NNTP) for newsgroups Email Services13

14 Post Office Protocol (POP) Created to allow for network-based access to mail stores Many early Windows-based mail clients used POP for access to Internet mail It allowed users to access UNIX-based mail servers It was the dominant type of mail server on the Internet before the rise of the Microsoft Exchange in the 1990s POP allows a central mail server to be managed to remain online at all times to receive mail for all its users Received mail is queued on the server until a user connects via POP and downloads the queued mail The user sends an e-mail through the mail server via SMTP Email Services 14

15 Internet Message Access Protocol (IMAP) Created to support some limitations of POP Keeping cached copies of user’s mails on the client, etc Created to support mail access in three modes: Online Offline Disconnected Email Services 15

16 POP and IMAP Basics POP and IMAP each need a server process to handle requests The server processes listen to ports 110 (POP) and 143 (IMAP) Each request to and from the server is in clear-text ASCII Email Services 16

17 Common POP Commands CommandDescription USER username Connects to POP3 server based on user name PASS password Enters the password for the user, as in PASS: Ax6yy LIST Displays the message number followed by the number of characters in the message UIDL Displays the unique ID for each message RETR n Replaces the n with a message number to retrieve that message TOP n lines Instead of retrieving the whole message, retrieves the number of lines designated by the lines parameter for message number n DELE n Deletes message number n from the server QUIT Ends the session Email Services17

18 Understanding POP3 More simplistic than IMAP4 First step is to log on with user name and password Can be used to: List mail Read mail Download mail Delete mail Email Services 18

19 Common IMAP Commands CommandDescription LOGIN username password Log on to the server with your user name and password, which are unencrypted. SELECT mailbox Select a mailbox before you perform mail tasks. The default mailbox is called inbox. The response gives a summary of mailbox information. FETCH message(s) item(s) Retrieve messages. The message(s) parameter gives the message number. The item(s) parameter determines what part of the message is fetched—that is, individual header items or the body of the text. STORE message(s) flags Change the flags associated with a message. Typically, this command is used to mark messages to be deleted, undeleted, or identified as unread. LOGOUT End the IMAP4 session. Email Services19

20 Understanding IMAP4/UW-IMAP The University of Washington’s IMAP4 and UW-IMAP implement both POP and IMAP protocols Its features include the following: Messages remain on server Requires much more space on server To keep track of the status of messages with flags such as: \Recent \Seen \Answered \Flagged \Deleted \Draft Email Services 20

21 Other Mail Service Issues Other issues with mail services include: SSL Security Availability Log Files Email Services 21

22 E-mail Clients Some e-mail clients include: WebMail – run on email provider’s web servers Elm (Linux) Alpine (Windows, Linux) Kmail (Windows, Linux) Mutt (Windows, Linux) Novell Evolution (Windows, Linux) Email Services 22

23 Configuring E-mail Clients Typical information required for configuring e-mail clients include: SMTP server IP address – outgoing server address Your e-mail address Your e-mail password POP or IMAP server IP address – the incoming server address the Exchange server and the University of Washington’s IMAP4 and UW-IMAP servers implement both protocols Email Services 23

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