The electronic mail is the transmission of message over the internet. E-mail is cheaper and faster than a letter and less intrusive than phone calls. It allows people to send messages to one or more recipient even the receiver is not logged in. The most common example of e-mail is a simple text message sent from one computer user to another type of network. Nowadays, some computerized company makes extensive use of e-mail because it is fast, flexible and reliable. E-mail can be much more than text, you can use e-mail to send files, documents, image, and programs. Anything can store electronically can be sent via e-mail. (Margarent Robbins and ED Tittel , E-Mail Essentials 1994)
When e-mail is received on a system, it is store in an electronic mailbox for the recipient to read later. There are several e-mail clients available like Thunderbird, Microsoft Outlook and Lotus. These software are configured with standard e-mail protocol to send and receive message, beside user can store their important message in the inbox of mail client. (C.B.Bayliss, 2000)
Some Internet Service Provider (ISP) offer e-mail and also support gateways so that you can exchange e-mail with other system. Usually, an e-mail takes about few seconds or minutes to arrive its destination. The recipient can reply or forward the message to their colleagues instead of typing a new same message.
The e-mail consists of many components and command which include the sender and receiver address. E-mail address is like "[email protected]", there is message which is the single piece of electronic information and the header of a message contains all the information that networked computer needs to transmit the message.
1.2 The use of e-mail
In the 21st century, individuals and organizations both large or small using e-mail networks that enable people to send anything from a short note to a long word-processing file, to one or many recipient. The e-mail transmissions can be held over land-based or wireless data link, or whether or not the sender and receiver use the same communications network. (Daniel J.Blum and David M. Litwack, 1995)
The uses of email include basic interpersonal messaging which is the day-to-day communication between people whether they are in workplace, travelling or home. Time savings resulting from e-mail are estimated one half hour or more per day per worker. The second is exchange of revisable files which mean word processing, graphic and application can be programmed to use the e-mail system. This eliminates the reformatting of information and boosts the quality of office output. (Daniel J.Blum and David M. Litwack, 1995)
The third one is electronic data interchange (EDI) which is organization can exchange formatted data containing quotes, purchase orders, shipping notices and invoice which can achieve savings and productivity improvement. This can benefit the organization higher quality products, e-mail allow employee to remain in better communication with other employee. EDI offers improved interface with both suppliers and purchaser. Also, it provide higher level of customer service for organization. Customer access to the appropriate goods and service, they can give feedback through e-mail for the company, at the same time staff assistance can be improved. Customer orders, trouble reports and customer information can be store in the corporate database, this providing a customer profile for future marketing and service efforts. (Daniel J.Blum and David M. Litwack, 1995)
1.3 Protocol
1.3.1 IMAP
The Internet Message Access Protocol (IMAP) is newer alternative to the POP3 protocol, it's a method of accessing electronic mail that are kept on a mail server, user can access to it with any computer configured with IMAP. The IMAP client program like Thunderbird and Microsoft Outlook can retrieve the message from server, also they can maintain a copy of the mail on local machine, the mail will remain on the server until user delete it. This mechanism allows multiple email clients access to a single mailbox, for example the IMAP server which store email can be manipulated from a desktop at home, workstation at office and a travelling notebook. The advantages of IMAP is allow message access and management from more than one computer, provide support for online or offline access modes and it's fully compatible with internet messaging standard.
(Rnejdl@Ring Of Saturn , 2007) / ( Marketing Department of NTC Hosting, 2002-2010)
http://corp.sonic.net/ceo/2008/01/22/imap-whats-that/
1.3.2 POP3
The Post Office Protocol (POP3) consist of two version, the first one is POP2 which is the standard in the mid-80's and require Simple Mail Transfer Protocol (SMTP) to send message. The second one is POP3; it can be used with or without SMTP. POP3 is a client/server protocol for receiving email. Email client like Thunderbird and Outlook check the inbox on the mail server and download any mail using POP3, POP3 is also an alternative to IMAP. Also, this standard is built-in some web browser like Netscape and Internet Explorer. POP3 is designed to handle offline operations, it download mail to computer and delete from the server. The disadvantage of using POP3 is it does not provide backup, once the mail downloaded to computer, the server do not have a backup of it.
(Webopedia ,2007) / ([email protected] ,2008)
http://www.tekguard.com/Content/Software/Tutorials/EMailTutorial_P2.htm
1.3.3 SMTP
The Simple Mail Transfer Protocol (SMTP) is a protocol use in email system for sending email. SMTP is use to send email among server to server or client to server. Besides, some email client use SMTP to send mail and either POP3 or IMAP for receiving email. SMTP is use to define the message format and the route procedure from source to destination through email servers. The extension for SMTP includes MIME (Multimedia Internet Mail Extension) support for non-text file including multimedia content. For certain company, the router port 25 has to be open to allow SMTP service. (Joseph Matthew ,2008)
http://14theories.com/index.cfm?page=support§ion=email
1.3.4 HTTP
The Hypertext Transfer Protocol (HTTP) is the protocol that used when user connect to a website over internet. Some email server provide web-based mail access which is user can browse manage their email through web browser. There is another enhanced HTTP protocol which is HTTPS (Hypertext Transfer Protocol Secure), HTTPS provide additional layer of security for user authentication. For example, hotmail provide web-based email access, user login with email address and password, the session is encrypted and secured.
(Ashwin Satyanarayana, 2009)
1.4 Server and Client
The mail server also known as Mail Transport Agent (MTA), it is a computer within a network that works as virtual post office. The mail server consists of storage where e-mail is stored for user, or a set of rules determine how mail server should works and react to the destination of a message. A computer dedicated to run such mail server application is called mail server like Microsoft Exchange Server, Exim and Qmail. The mail server works with other client program like Outlook and Thunderbird to form a messaging system. When a user send an e-mail, the message handle by Mail User Agent (MUA) forward to the mail server within local network, the server will forward the message to another system or network according to destination address. The protocol use for sending mail is Simple Mail Transfer Protocol (SMTP), and the protocol for receiving email is Post Office Protocol (POP3) and Internet Message Access Protocol (IMAP).
(Daniel E.Singer ,2006) / (Webopedia ,2004)
The mail client is an application that runs on a personal computer or workstation which enable user to send, receive and organize e-mail. There is license require Microsoft Outlook or open source client like Thunderbird and Lotus available. It's called client because e-mail system are based on server-client architecture. An email is sent from any client to a central server, and the server decides where to route to the destination. An email client also called Mail User Agent (MUA), it consist of receiving protocol like POP3 and IMAP. Email client will download the latest inbox message to local computer, and it will remain the original of email on mail server, user can manage their email inbox through client application. In addition, there are also web-based email programs like Gmail, Zimbra, Hotmail and Yahoo Mail. These mail server provide free-of-charge registration and mail service for end-user, user can manage their inbox through web-browser instead of using email client application.
(Webopedia, 2002) / (wordIQ.com ,2010)
1.5 How Email Works
The e-mail create by a sender, a user can compose new message via web-based mail server or Mail User Agent (MUA) like Outlook or Thunderbird. When the email is sent, the message is routed from server to server, all the way to the recipient's email server. Also, the message is sent to the mail server tasked with transporting emails called Mail Transport Agent (MTA). The MTA communicate with another server using protocol SMTP and so call SMTP server.
(Jeff, 2008)
The recipient's MTA delivers the email to incoming mail server called the Mail Delivery Agent (MDA) which stores the email on the server and wait for the user to retrieve it. There are two protocol used to retrieve email on MDA which is POP3 and IMAP. (Jeff, 2008)
On real-world analogy, MTA act as the post office which handle message transportation while MDA act as mailbox which store message and until the recipient check the mailbox. This means that recipient not necessary to be online for them to send or receive mail. Besides, the process of retrieving message is done using software called MUA. (Kavi, 2005)
1.5.1 Mail Transfer Agent (MTA)
The Mail Transfer Agent(MTA) sends, receive and delivers mail between servers with Exchange System. The MTA receives messages from various sources. As each message is received, the MTA decides where and how the message should be routed. Sometimes the network administrator may experience problems with the MTA, the MTA fails to start due to a corruption or crash, than the MTACHECK utility will have to be used. The MTACHECK verify the validity of objects use by MTA to deliver message. These problem include message stuck in an inbound or outbound queue. Many modern email client program can act as MTA when sending email, these client are authorized to use and do not directly deliver the message to the intended recipient's mail server.
(Red Hat, Inc, 2007) / (Kevin Johnson, 2000) / (Adesh Rampat, 2001)
http://www.x-trend.ch/dienstl/messaging/sendmail.htm
1.5.3 Mail Delivery Agent(MDA)
Once the Mail Transfer Agent(MTA) has received a message, processed it and decide where to route it, it pass to an Mail Delivery Agent(MDA). The MDA is responsible for delivering a message to another location, which could be another MTA, a user's inbox or a program that performs a special task. The simplest type of MDA is used by some system to deliver to a local mailbox. The MDA appends the incoming message to a local user's inbox. Also, some MDA provides filtering features that have additional manipulation of incoming messages. In general, MDA do not transport message between systems nor do they provide a user interface. (Kevin Johnson, 2000) / (Red Hat, Inc, 2007)
1.5.2 Mail User Agent(MUA)
While Mail Transfer Agent(MTA) and Mail Delivery Agent(MDA) are responsible for routing and transporting mail messages, Mail User Agent(MUA) are responsible for providing an interface for users to manage their mail. This management include viewing message, managing mail folders, and composing and sending new mail, as well as replying to message folders and sending existing message to other user. There are two types of MUA which the first one is an email sent from an Internet Service Provider(ISP) is handle by ISP's mail server. Once the mail deliver to the destination, the recipient pick up the mail by using his or her email program connected to the mail server and request for the item in inbox. The second type is web-based; in this case an email program is built into a website for public use. The server holds many accounts that user can access through providing username and password, once logged into a mailbox, the user can manage their inbox on web browser. For example Hotmail or Gmail provide free account register for user, they can manage through web-based mail programs. (Kevin Johnson, 2000) / (Red Hat, Inc, 2007)
1.6 Email message components
The first component is subject line. The subject line is the first thing seen when email arrives in the inbox. It will also be the biggest factor determining whether the e-mail will be opened, some spam mail contain words like "Free" in subject line, so most user choose not to open the message. The figure below show the subject line at top, actually subject line is also the subject or the purpose of the whole message.
The second component is the header section. There is "From" and "To" field. It is also a factor determining whether the email will be opened. The "From" field show the sender name and e-mail address and the "To" field show the recipient name and address.
The third component is the body of the message. The body section consist of text entered by the sender, normally it's text to convey the actual message sent to a recipient. At the end of the message body that convey information about the sender.
1.7 Email Security
Email security is a priority for all business, with the growing threat of hackers, virus spam, phishing and identity theft is some of the security loophole on email service. Email security is a multi-layered discipline which involves using several security software and security technology.
1.7.1 The lack of Security in E-mail
E-mail is inherently insecure. In this paragraph I will show how insecure is it. The first one is webmail; webmail is also known as web-based email program like Hotmail and Gmail. If the connection to the webmail server is insecure the URL of the browser should be http://" and NOT "https://, this mean that all information including username and password is not encrypted as it passes between the Webmail server and user's computer.
The second one is Simple Mail Transfer Protocol (SMTP). SMTP does not encrypt messages; communication take place by SMTP server may send user's messages in plain text for any eavesdropper to see. Also, some SMTP server require user to login with username and password in order to relay messages to other server, these information is also in plain text format which can also sniff by hackers. Lastly, message send via SMTP include information about which computer they were sent from and what email program the sender used. This information is available to all recipients; it may be a privacy concern.
The third one is Post Office Protocol (POP3) and Internet Message Access Protocol (IMAP). The POP3 and IMAP require user to key in username and password to login, this credentials are not encrypted. In this case, the messages and credentials can be read by any eavesdropper between user computer and email server.
The last one is Backup of Email. Email message are stored on SMTP servers in plain, unencrypted text. Backup of these data may be made at any time by administrator. Administrator can read any data on the machine which mean the message sent out by a user may be saved unexpectedly or may be read by unknown person.
1.7.2 Encryption of Transmission
Most email messages a user sent travel long distance over many network, secure and insecure, monitored and unmonitored, the email message passing through and making copies of themselves on servers all over the internet. To avoid the message read by someone, we might want to encrypt the email from prying eyes. Pretty Good Privacy (PGP) is software that protects credit cards number and information that can be used to commit identity theft. With encryption on email message, only the intended recipient will be able to open and read the message. In addition, there is also another way to encrypt the e-mail message which is using symmetric encryption. In symmetric encryption, the sender and the recipient share a "secret key". Using this key, you can encrypt a message into "cyphertext". Cyphertext is a random sequence of character which is completely meaningless to anyone unless they have the secret key. If a user with the secret key, he can decrypt the cyphertext into an original message and read it. The below picture show that the user compose a new mail message, and then he have to decide a secret key and use that key to encrypt it, after encrypt the message is in cyphertext form and pass to recipient, the recipient have to use the secret key by the sender to decrypt it and read the original message.
(Erik Kangas, 2009)
http://luxsci.com/blog/the-case-for-email-security.html
1.7.3 Attachment Scanning
Email attachments are used by attackers for spreading malware and viruses. If you receive an email from friends, colleague or relative, it is best to exercise caution before opening any attachment. Sometimes the sender's computer is compromised by malware or viruses, these malware spread into the address book of the user and it will spread the viruses to all of the contact. For example, there is a malware which will auto spread to a user's contact list without knowing by the sender. As you can see the below picture is taken by the author, the red circle URL links is a malware website, once the recipient click on it, his or her computer will infected. (Silki, 2010)
Nowadays, modern web based client like Hotmail and Gmail have a virus scanning utility which will scan any attachment before the recipient download them. Besides, if email client doesn't have this utility, user can choose to use a free service named Virus Total which can scan malware or viruses in attachment.
1.7.3.1 Ways to handle attachment wisely
There are several ways to handle attachment wisely which the first one is don't open any attachment you were not expecting, even it comes from a trusted source, relative or friends. The second one is if recipient don't know the source of any email message, you are advised not to open the message include attachment, always delete the message without reading it. (Indiana University, 2010)
The third one is recipient might receive attachment with .exe, .vbs or .ink. Normally this kind of file is considered malware or viruses. Once the users execute these file, the user's computer might get infected. The last one is never open any attachment unless you verified it is virus free. User can download the attachment to their hard drive and scan it with Anti Virus software like Avira, Symantec End Point to make sure the file is clean. (Indiana University, 2010)
1.7.4 Email user or staff policy
For certain business or organization they can have email security policies to enhance the security level of the network from email service. Business can train their company staff in the basic email usage rules and best practices, such as not opening email from unknown source or clicking website URL that you can't trust. Besides, staffs are advised to use bbc option with integrity, so that spammer cannot get large list of name, forward and reply button are two other practices that can help secure business communication. In addition, email and computer login should be based on strong password, rather than ones are easy to guess. Password should be change regularly to maintain security.
(Arif Mohamed, 2009)
1.8 Security Threats to E-mail
1.8.1 Spam
Since the World Wide Web was created, resources have become more accessible and flow of information circulating on the network. At the same time, people have quickly learned how to wrongly make use of these resources. "Spam" refers to sending of unsolicited bulk e-mails. People who send bulk advertising e-mails are called "spammers". The spam's primary goal is to advertise at the lowest price via "junk-mail". Spammer sometimes claims, in bad faith that their recipient spontaneously signed up to their database and that the received e-mail is easy to delete. (Jeff, 2008)
In this paragraph, it will describe how spammers work. Spammers collect e-mail address from the internet like forums, websites, and discussion groups. There is software named "robots" that browse various pages and store all of the e-mail address that appear them in a database. After getting that e-mail address, spammers only has to lunch an application that send each address the advertising message. (Jeff, 2008)
The above picture shows an example of spam message. As you can see that the source is from greeting-cards.com. The content is about the recipient's friend sending him/her postcards. If the recipient want to view the postcard they have to click on the links, once they click on the links they are infected.
http://www.mydigitallife.info/2007/07/22/virus-via-greeting-card-notice-another-new-trick-from-spammers/
1.8.1.1 Drawbacks of Spam
Spam mean sending bulk email to a recipient, the recipient email inbox will be flooded and the space takes up in victim's mailbox. Secondly the recipient might face difficulty consulting personal or professional messages mixed with the advertising messages and increased risk of mistakenly deleting or not reading important messages. (Jeff, 2008)
Thirdly, spam will waste the bandwidth usage on the network and it takes time for administrator to set-up anti-spam system. At the same time, administrator try to choose alternative way to secure network security which is using additional resource by installing Microsoft Exchange Server or other licensed security software. (Jeff, 2008)
1.8.2 Eavesdropping
Since email typically travels over the network, it is subject to eavesdropping. This can be very easy to do, depending on the network environment. Many network interface card provide ability to view all network packets on network segment, not just the packet going to and from the machine. This eavesdropping is sometimes called snooping or sniffing, and any data transmitted in plain text is subject to it. Eavesdropping mean someone on the internet reading an unknown source and destination email message. The problem of eavesdropping is not limited to a local network but it exists at all point between the client and server. (Kevin Johnson,2000)
1.8.3 Denial of Service
Denial of service (DoS) means prevent a service from being operational. They are used primarily for two purposes which is preventing a service from being operational and to coerce vulnerability in a system. Attacker attempts to prevent users within organization accessing information or services. The most common type of DoS attack occur when an attacker flood the network with information. For example when a user type an URL in browser, the browser will request information once from the server, but if an attacker overloads the server with request, the server can process the queue of request by other user causing the access to website is disable.
In addition, an attacker can use spam email messages to launch similar attack on email account. For example we can subscribe to Hotmail or Gmail free service, every user is assigned with a specific quota which limits the amount of data you can have in your account. Attacker can modify the quota limit of an account smaller, when the users are about to receive big file from his or her friend, so the email server will rejected it, causing the recipient cant receive any attachment email. (Mindi McDowell, 2004)
1.9 Email service
1.9.1 Web-based
With web-based email, use can use browser to go to email provider site, the log in with username and password. The email provider stores all message on the server, web-based email is easy to implement and can bring repeat visitor to the website. Some of the email provider offer extra features like spell-checkers or personal address book. The benefit of using web-based email is that user can access to it using a computer with web browser and it is also great for people who do not own a computer. They can access to their inbox when travelling or in college.
http://www.emailaddresses.com/guide_types2.htm
1.9.2 Email forwarding
Email forwarding mean forward message to another existed email address. It offer transfer message information between accounts. This can be handy if you have a web-based email account, user don't have to surf to website each day to check your mail. By using forwarding service, the mails receive at the website will automatically forward to your preferred email address. Email forwarding service provide convenience for people who change their email address regularly and help keeping main email address private, and still collecting all mail in one place.
(Mindi McDowell, 2004) http://www.wisegeek.com/what-is-email-forwarding.htm
1.9.3 POP Mail
Post Office Protocol (POP) store incoming message on a server until the recipient ready to collect them. Those email messages can be downloaded via email client programs like Thunderbird or Microsoft Outlook. Once the message is downloaded to client program, user can choose to delete the one on server or still maintain on server to maintain backup of message. Also, POP mail offer offline work mode, which mean user can compose a new message and store as draft, when the computer is online user can send it to destination.
1.10 Benefit of e-mail
1.10.1 Business
The e-mail brings a lots benefit to business organization in several ways. The first one is speedy information transfer, for certain large company, proper communication is very difficult to achieve. E-mail brings solution to overcome these problems. For example, a company's staff want to announce their other branch something, so what a staff need to do is compose a new mail message and click send, the email will be blaze through the network at amazing speed, within few minutes then message is deliver to destination. E-mail provides almost real-time update status and rapidly disseminates information to multiple employees at same time.
The second benefit is that e-mail help decrease cost. The cost to maintain an email system is low, company can utilize free online email service for no cost beyond their computer and internet connection expenses. Company just has to pay internet connection fees monthly, but the expenses on postage, telephony and travel expenses are reduced.
The third one is decrease layer of management. Employee in a company can email the company president with idea, suggestion or comments. Management can obtain opinion from front lines of their business, which helps them stay in touch day to day operations. Besides, suggestion and idea obtain from employee can help innovate the business or even create a new revenue stream for the business. (Laura Acevedo, 2010)
The last one is security. The email considered the most secure method of communication compare to letters and faxes. If paper falls into someone hands, it might harmful to the company. If faxes containing confidential information left on faxes machine, it may also used wrongly by other people. Thus, emails are recommended to use in business because it ensure the security of information, record and details, anything send out or receive by a company remain a copy on server. (Stephen Rampur, 2009)
Chapter 2 : Ubuntu Server Operating System
2.1 Feature and Specification
2.1.1 Reduce Cost
Ubuntu Server Edition is an opportunity for business to achieve real savings on IT infrastructure. Ubuntu Server Edition include what is needed to provide a service which is less computing power and less resource required. Also, Ubuntu Server offer fewer components for administrator to maintain in simple steps. In addition, Ubuntu Server also offer automatic update after installation of the operating system, when the server connect to internet it can simply update the latest change of service or application from internet. Ubuntu Server offer packaged installation which is most service on a server is packaged administrator can start, stop or shut down the service with a single command. Unlike other Linux system, the application and dependencies require it to run it are "packaged" together. Lastly, Ubuntu Server provide free of licensing and subscription fees. In fact, the Ubuntu Server security team provides vital maintenance and security updates for free.
2.1.2 System Integration
Ubuntu Server fits easily to existing client or server architecture, integrated with commonly-used tools for authentication and service access. Beside, to integrate with system using Microsoft Active Directory, all supported version of Ubuntu Server come with Likewise-Open. Likewise-Open help Ubuntu Server to share information, resource with machine on Active Directory. Lastly, Ubuntu Server offer share print and file sharing service. There is a application named SAMBA (an open-source implementation of SMB/CIFS) which will automatically discovery of printing resource and handle file sharing on different platform like Window and Linux.
2.1.3 Security
Ubuntu Server come with built-in security, it has security at the core and built upon the renowned security of the Debian Operating System. Also, Ubuntu Server includes easy-to-use security features which can reduce the element of "user error" in security management. Ubuntu Server had no open ports by default, so there is no danger service running without an administrator's knowledge. Besides, Ubuntu Server offer access control with AppArmor which allow administrator to associate each program with security profile and control the authority and right of that program. Another feature is that administrator can create an encrypted private directory where you can store critical information.
2.2 Ubuntu Server tools to setup Email System
Domain Name System (DNS)
Domain Name System(DNS) is commonly used on the internet and local networks, DNS is used to resolve names of systems into IP address and vice versa. System using IP networks must know the IP address of a remote machine in order to connect to it. In fact, most user prefer using names of machines such as hostname or fully qualified domain name (FQDN) to specify a system and connect to it. Thus, DNS was implementing in a network to do translation of IP address to hostname and vice versa. For example, a client in network request information from name server, this connection is using port 53. The DNS will refer to its library which may contain information about the host requested or cached data about the host earlier query. If the DNS can't find any information from library, it will request to other DNS server called root DNS server and respond the information back to the client.
Berkeley Internet Name Domain (BIND)
Berkeley Internet Name Domain (BIND) is an implementation of Domain Name System (DNS) protocols and provides reference implementation of the major components of Domain Name System include DNS Server, DNS resolver library and tools for verifying the proper operation of DNS server.
Apache
Apache is the HTTP-server which most used web server for a Linux System. A web server like Apache, is software that display and serves HTML page hosted on a server to a client browser that understand the HTML code. The most common protocol used to transfer Web Page in Hyper Text Transfer Protocol (HTTP) and File Transfer Protocol (FTP), a protocol used to uploading and downloading files are also supported in Apache. Apache server are often used in combination with MySQL database engine and HypetText Preprocessor (PHP) scripting language. A configuration termed LAMP (Linux, Apache, MySQL, PHP) is recommended for development or deployment of web-based application.
Email Server Dovecot and SendMail
Dovecot is an open-source Internet Message Access Protocol (IMAP) and Post Office Protocol (POP3) email server for Linux system. Dovecot is recommended for both small and large installation of email system. It's fast, simple and easy to set up and requires no special administration and uses little memory. There are few features in Dovecot which is Dovecot is self-healing, it will fix most of the problem notice by itself such as broken index files. The problem will be logged and later administrator can figure out what cause them. SendMail is also used to set up email system, SendMail act as Mail Transport Agent (MTA) responsible for sending any email message. SendMail support many kinds of mail transfer and delivery method include Simple Mail Transfer Protocol (SMTP).
2.3 Ubuntu Server Operating System Requirement
Minimum Requirements
Server
Desktop
Processor (x86)
300Mhz
1Ghz
Memory
128 MB
512 MB
Hard Drive (Free Space)
1 GB
5 GB
Monitor Resolution
640 x 480
1024 x 768
Chapter 3 : Comparison of Server
Windows vs Ubuntu Server
Ubuntu Server vs Ubuntu Desktop
Types of email server
Gmail and Hotmail
Email Client
