E-mail transfer mechanism

E-MAIL TRANSFER MECHANISM : E-MAIL TRANSFER MECHANISM 1

Slide 2 : On the completion of this topic, you would be able to understand : E-mail Protocols. User Id and Password. E-mail etiquettes. MIME attachments. E-mail security. 2

Electronic mail : Electronic mail 3 Major components: User agents Mail servers Mailboxes Protocols: Simple Mail Transfer Protocol (SMTP) delivers mail to servers. From clients to local mail server. Inter-mail server delivery. Post Office Protocol (POP) for user access to delivered email.

Slide 4 : 4 POP POP Fig .1

Electronic Mail servers : Electronic Mail servers 5 Servers maintain: A message queue of outgoing email messages . A mailbox containing incoming messages for each user. SMTP protocol runs between mail agents and servers to send email messages Client — the sending mail server or agent. Server — the receiving mail server.

Slide 6 : 6 POP POP Fig .2

Electronic MailThe email delivery process : Electronic MailThe email delivery process 7 Mail Sender Protocol flow Email flow LocalMail Server Fig .3

Electronic MailThe email delivery process : Electronic MailThe email delivery process 8 User’s mail agent contacts its local mail server. Local mail server contacts the destination mail server(s). Destination mail server places the mail into the appropriate user’s mailbox. User retrieves mail via a mail access protocol.

The Email Delivery Process : The Email Delivery Process 9 SMTP uses a TCP socket on port 25 to transfer email reliably from client to server. Email is temporarily stored on the local server and eventually transferred directly to receiving server. Intermediate relay is a special case. Three phases of the protocol: Handshaking (“greeting”). Transfer of messages. Closure.

Electronic MailMail message format : Electronic MailMail message format 10 Header lines From: To: Subject: Body The “message”, ASCII characters only. header body blank line

Mail Message FormatMIME — Multimedia mail extensions : Mail Message FormatMIME — Multimedia mail extensions 11 SMTP requires all data to be 7-bit ASCII characters. All non-ASCII data must be encoded as ASCII strings. Additional lines in the message header declare MIME content type.

Slide 12 : 12 From: rajuroyal009@gmail.com To: venkey.arya@yahoo.co.in Subject: Picture of yummy crepe. MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Type: image/jpeg base64 encoded data ..... ......................... ......base64 encoded data

User Ids and Passwords : User Ids and Passwords User Id It is used to identify you to the computer. Also known as User name or Account Name. Password A secret code that authenticates you to the computer. A password should be easy for you to remember and difficult for others to guess. 13

Hints for a good password : Hints for a good password A good password should Be at least 8 characters long. Contain alphabets and numbers. Include non-alphabetical symbols (%,&,! etc). Posses UPPERCASE and lowercase letters. 14

E-Mail Etiquette : E-Mail Etiquette Etiquette – is defined as: “the conduct or procedure required by good breeding or prescribed by authority to be observed in social or official life”. Network etiquette is the etiquette of cyberspace. In other words, Netiquette is a set of rules for behaving properly online. 15

General Netiquette : General Netiquette Internet etiquette. Meaningful subject Use uppercase and lowercase letters. Check spelling. Be careful what you send. Be polite. Be cautious with sarcasm and humor 16

E-Mail Etiquette : E-Mail Etiquette Things to do when sending e-mail: Keep emote icons to a minimum; i.e.., :). Use spell checking. Most e-mail software packages have spell checking and it can be set to check each message before sending. 17

E-Mail Etiquette : E-Mail Etiquette Things to do when sending e-mail: Zip attached files. Three reasons for this: Reduces file size. Protects against firewalls stripping attachments. If multiple attached files, makes easier to unpack. 18

E-Mail Etiquette : E-Mail Etiquette Things to do when sending e-mail: Before sending large attachments, send a short message to the recipient informing them of what you are about to do, and wait for their response. Remember we still have people on dial-up 19

E-Mail Etiquette : E-Mail Etiquette Things to do when sending e-mail: Be sure to complete the subject line of the email, and please do not use the following as subjects: Hi HAPPY NEW YEAR TO YOU MY DEAR FRIEND!!!! 20

E-Mail Etiquette : E-Mail Etiquette Things to do when sending e-mail: Remember the written word, unlike a conversation, can be interpreted/mis-interpreted very easily. Choose your words carefully. 21

E-Mail Etiquette : E-Mail Etiquette Things to do when sending e-mail: Also, do not capitalize (i.e.., ALL UPPERCASE) unless you really mean it. “CALL ME!” is interpreted differently than “call me.” 22

E-Mail Etiquette : E-Mail Etiquette Things to do when receiving e-mail: Even if you don’t have time to “fully” respond to an email, be sure to let the sender know you have received it!. 23

Netiquette : Smileys : Netiquette : Smileys Use smileys and text messaging shorthand cautiously Use the Bcc function for group mailings Don’t send replies to all recipients Don’t send huge attachments Explain attachments Stay alert for viruses Notify recipients of viruses 24

E-mail Security : E-mail Security Spam. Phishing. Virus. Junk Mail 25

Spam : Spam Spam is unwanted electronic junk mail about medical products, low-cost loans, and fake software upgrades that arrives in your online mailbox. A spam filter is a type of utility software that captures unsolicited e-mail messages before they reach your inbox. 26

How to control Spam ? : How to control Spam ? Never reply to spam when you receive it. Don’t click links in e-mail messages, eve if its an opt-out links. Give your e-mail address only to people from whom you want receive e-mail, be wary of providing your e-mail address at web sites ,at web sites ,entering it on application forms, or posting to in public places such as online discussion groups. 27

Phishing : Phishing Phishing is an e-mail based scam designed to persuade you to reveal confidential information, such as your bank account number or Social Security number. If you don’t want to become a phishing victim, be suspicious of e-mail messages that supposedly come from banks, ISPs, online payment services, operating system publishers, and online merchants. 28

How to avoid Phishing ? : How to avoid Phishing ? Use antispyware utilities to clean up any spy ware that might be on your computer. Run antispyware continuously just as you do antivirus software. Set your browser to reject third-party cookies. Register to reject flash cookies. Install an antispoofing tool to help you identify fake web sites. Set up a disposable e-mail address and use it as necessary . Do not click links in untrusted e-mail or pop-up ads, and never respond to e-mail offers, especially those that seem too good to be true. 29

Email Virus - Melissa : Email Virus - Melissa May 24, 1999, Melissa virus is spreading as RTF files. 300 organizations affected, 100,000 hosts. One site reported, 32,000 copies of email are received in 45 minutes. Not a worm, require user interaction to propagate the virus. Why called Melissa? Named by the antivirus software vendors. Don’t open attachment ? not infected. 30

Junk Mails : Junk Mails How can they get into your mailbox? From name card, letter heads, published papers. Use search engine in the newsgroup, bulletin boards, phone books. Dump a full user list in a server. How to stop the intrusion of Junk Mails? Mail server providers joint effort. Filtering. Preview before downloading. 31

E-mail Terminology : E-mail Terminology Autoresponders (Mailbots): Automated programs that are established to return a prewritten message upon receipt of e-mail. Aliasing (redirecting): Using a fictitious address with which to send and receive e-mail. Typically done to avoid long "real" e-mail addresses. Bounced Message: A returned, can't deliver e-mail message. 32

Slide 33 : 33 Encoding: A method of sending binary (non-text files) with e-mail messages. Flame: An angry or rude e-mail message, often posted as a public response on a discussion group. Header: The first part of a received e-mail message that contains information about the routing of the message while traversing the Internet.

Slide 34 : 34 Lurk: To observe an online discussion without participating. Good idea when first joining a Mailing List. Mail Bomb: Hundreds or thousands of e-mail messages sent to the same address, causing an avalanche effect. Mailer Daemon: A Unix program used in the management of e-mail messages.

Slide 35 : 35 Mailing List: A collection of e-mail addresses of people who have asked to receive regular mail discussions on a particular topic. Mailing List Manager: An automated program to handle the administrative functions of adding/removing subscribers, disseminating the message postings. Moderator: Someone who controls the postings of messages in a Mailing List to ensure conformity with the topic and list policies.

Slide 36 : 36 Netiquette: Network Etiquette. Acceptable practices of using various Internet resources. SMTP: Simple Mail Transfer Protocol. The most common protocol used for transferring e-mail across the Internet. POP/POP3: Post Office Protocol. A mail protocol used to service intermittent dial-up connections to the Internet. IMAP (Internet Mail Access Protocol): A method to access and manipulate e-mail that is stored remotely on another computer.

Slide 37 : 37 Postmaster: The person to contact at a particular server/site to get help, or information about that server/site. Signature Line: A set of 4 - 8 lines of text placed at the end of a mail message to provide the reader with the author's contact information. SPAM: To send unsolicited commercial e-mail, usually in large amounts and indiscriminately, to discussion groups or subscriber bases.