The University of AkronSummit College

Business Technology Dept.2440: 141

Web Site Administration

Email ServicesInstructor: Enoch E. Damson

The E-mail EnvironmentE-mail evolved from a variety of proprietary systemsIn the 1980s and 1990s, people often had e-mail addresses on

a number of systemsThe standard for current e-mail services is to use DNS with a

special Mail Exchange recordThe Mail Exchange record contains the IP address of the mail server for

a domainTo allow users to send images, video, audio, and other binary

files via e-mails, the Multipurpose Internet Mail Extension (MIME) specification was developed

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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)

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Role of DNS in E-mail SystemsA domain name, such as example.org, needs to be

associated with two IP addressesOne IP address can be for a Web siteAnother 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

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E-Mail ProvidersEvery email provider supplies three fundamental

services:Send emailReceive emailStore received email at least temporarily

Difference between email providers and their cost depends on:VersatilitySecurityExtent of services

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E-Mail ServicesE-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

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E-mail ProtocolsThe 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 accountsEmail Services 7

Simple Mail Transfer Protocol (SMTP)The main standard for mail transport across the InternetDefines the method of sending mail from a host to anotherIts major strengths include its:

Simplicity Platform-independent

Requires that a host be capable of sending ASCII text to another hostTypically done using port 25 (SMTP) on a mail server

E.g. telnet mailserver 25

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Common SMTP CommandsSome major SMTP commands include:

HELO – used by clients to introduce themselves to the server (originating hostname) E.g. HELO example.org

VRFY– verifies the email userDATA – specifies the body of the messageQUIT – ends the SMTP session

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Common SMTP HeadersMajor SMTP headers include:

MAIL FROM: – informs the mail server about the email’s origin (sender’s email address) E.g. MAIL FROM: someone@example.org

RCPT TO: – specifies the receiver’s email address E.g. RCPT TO: customer@example.org

RECEIVED: – identifies the email server that processed the messageDATE: – indicates the date of the emailSUBJECT: – shows the subject of the email messageTO: – shows the recipient of the email messageCC: – sends copies of the message to a list of email addresses

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Sample SMTP SessionHELO WKS1250 web1.technowidgets.com Hello [127.0.0.1]MAIL FROM: XYZ@yahoo.com250 2.1.0 xyz@yahoo.com....Sender OKRCPT TO: cbranco@technowidgets.com250 2.1.5 cbranco@technowidgets.comDATA354 Start mail input; end with <CRLF>.<CRLF>This is a simple message.QUIT

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Installing and Administering Microsoft ExchangeThe Microsoft Exchange Server can be much more than a

simple e-mail serverIt 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

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Microsoft Exchange FeaturesThe 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 MessagingNewsgroups

Requires the Network News Transport Protocol (NNTP) for newsgroups

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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 1990sPOP allows a central mail server to be managed to remain

online at all times to receive mail for all its usersReceived mail is queued on the server until a user connects via POP and

downloads the queued mailThe user sends an e-mail through the mail server via SMTP

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Internet Message Access Protocol (IMAP)Created to support some limitations of POP

Keeping cached copies of user’s mails on the client, etcCreated to support mail access in three modes:

OnlineOfflineDisconnected

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POP and IMAP BasicsPOP 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

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Common POP CommandsCommand Description

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

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Understanding POP3More simplistic than IMAP4First step is to log on with user name and passwordCan be used to:

List mailRead mailDownload mailDelete mail

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Common IMAP CommandsCommand DescriptionLOGIN 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.

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Understanding IMAP4/UW-IMAPThe University of Washington’s IMAP4 and UW-IMAP

implement both POP and IMAP protocolsIts features include the following:

Messages remain on serverRequires much more space on serverTo keep track of the status of messages with flags such as:

\Recent \Seen \Answered \Flagged \Deleted \Draft

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Other Mail Service IssuesOther issues with mail services include:

SSL SecurityAvailabilityLog Files

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E-mail ClientsSome e-mail clients include:

WebMail – run on email provider’s web serversElm (Linux)Alpine (Windows, Linux)Kmail (Windows, Linux)Mutt (Windows, Linux)Novell Evolution (Windows, Linux)

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Configuring E-mail ClientsTypical information required for configuring e-mail

clients include:SMTP server IP address – outgoing server addressYour e-mail addressYour e-mail passwordPOP 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

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