CIT 140: Introduction to ITSlide #1 CSC 140: Introduction to IT Electronic Mail

CIT 140: Introduction to ITSlide #2 Topics What is ? Protocols Addresses Headers UNIX Applications –mail –pine –KMail

CIT 140: Introduction to ITSlide #3 What is ? A method of composing, sending, and receiving messages over electronic communication systems.

CIT 140: Introduction to ITSlide #4 Transfer Dialog

CIT 140: Introduction to ITSlide #5 Protocols: Sending Simple Mail Transfer Protocol (SMTP) –This dictates the format of the message in terms of an envelope, a header and a body and facilitates the movement of the message between the components of a typical transfer. Domain Name System (DNS) –This dictates the exact form of an address.

CIT 140: Introduction to ITSlide #6 Example SMTP Session S: ESMTP Postfix C: HELO mydomain.com S: 250 Hello mydomain.com C: MAIL FROM: S: 250 Ok C: RCPT TO: S: 250 Ok C: DATA S: 354 End data with. C: Subject: test message C: From: C: To: C: C: Hello, C: This is a test. C:. S: 250 Ok: queued as C: QUIT S: 221 Bye

CIT 140: Introduction to ITSlide #7 Protocols: Receiving Post Office Protocol (POP) or Internet Message Access Protocol (IMAP) –Works best for offline reading from a single host computer that contains your . Multipurpose Internet Mail Extensions (MIME) –This dictates the format of multimedia files used as attachments to an message.

CIT 140: Introduction to ITSlide #8 History of –First on mainframe systems like CTSS –Internet started. –First messages sent on Internet –First spam message sent from a DEC engineer –RFC 788 published, describing SMTP –DNS released, allowing

CIT 140: Introduction to ITSlide #9 Addresses Bang Paths –utzoo!decvax!harpo!eagle!mhtsa!ihnss!ihuxp!grg –Recipient: grg –Recipient’s machine: ihuxp –Machines connected by modems at night to avoid long- distance charges. –Transmission times measured in days.

CIT 140: Introduction to ITSlide #10 Addresses –Top level domain: edu Limited: com, edu, gov, net, org, country codes Internet Assigned Numbers Authority (IANA) ICANN controls IANA –Subdomain: nku Allocated by top-level domain administrators. –Hostname: cs Allocated by subdomain administrators. –Username: jw Allocated by hostname administrators.

CIT 140: Introduction to ITSlide #11 Headers To: contains address(es) of recipient(s) From: contains the address of sender. Cc: address(es) of additional recipient(s). Date: Date and time at which message was sent. Attch: lists any attachments that might accompany the message, usually in the form of external files. Subject: indicates the subject of message. Received: tracking information indicating which servers handled the message.

CIT 140: Introduction to ITSlide #12 Example Headers From Thu Sep 15 06:03: Received: from mailapp0.msomt.modwest.com (mailapp0.msomt.modwest.com [ ]) by smtp.utoledo.edu (8.14.7) with ESMTP id j8FA for ; Thu, 15 Sep :03: (EDT) Received: from nat.dd-b.net (HELO rafael) ( ) by mpls-pop-13.inet.qwest.net with SMTP; 15 Sep :06: X-Sender: (Unverified) X-Mailer: QUALCOMM Windows Eudora Pro Version Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed X-Modwest-MailScanner: Found to be clean Message-ID: Date: Thu, 15 Sep :05: Reply-To: Bruce Xyzzy From: Bruce Xyzzy Subject: CRYPTO-GRAM, September 15, 2005 To: Precedence: list

CIT 140: Introduction to ITSlide #13 Attachments historically used 7-bit ASCII. Binary files, such as images or programs, require 8 bits of data per byte. MIME –Encodes 8-bit files as 7-bit ASCII. –Stores multiple files with a single message. MIME Headers –MIME-Version: 1.0 –Content-type: text/plain –Content-transfer-encoding: base64

CIT 140: Introduction to ITSlide #14 MIME Message Example Content-type: multipart/mixed; boundary="frontier" MIME-version: frontier Content-type: text/plain This is the body of the message. --frontier Content-type: application/octet-stream Content-transfer-encoding: base64 gajwO4+n2Fy4FV3V7zD9awd7uG8/TITP/vIocxXnnf/5mjgQjcip BUL1b3uyLwAVtBLOP4nV LdIAhSzlZnyLAF8na0n7g6OSeej7aqIl3NIXCfxDsPsY6NQjSvV 77j4hWEjlF/aglS6ghfju FgRr+OX8QZMI1OmR4rUJUS7xgoknalqj3HJvaOpeb3CFlNI9V GZYz6H6zuQBOWZzNB8glwpC --frontier--

CIT 140: Introduction to ITSlide #15 Privacy is transmitted through several MTAs on its way from sender to recipient. – can be read on disk of mail server. – can be read in transit using a sniffer. Additional privacy issues –Your address is included in headers. –Your server is displayed in headers.

CIT 140: Introduction to ITSlide #16 Threats Snooping –Others reading your . Spoofing –Forging to appear to be from someone else. Identity Theft –An attacker impersonates you or someone you know by spoofing to appear to be from them. –Phishing Repudiation –Since attackers can impersonate others in , people deny sending they actually wrote. Fraud –419 scams.

CIT 140: Introduction to ITSlide #17 Security Measures Encrypt in transit. –SSL encryption for POP, IMAP, SMTP. –Many clients and servers support. –Also SSL encryption for webmail. Encrypt before transit –PGP and S/MIME (incompatible with each other.) –Must exchange cryptographic keys with recipient. – encrypted in storage and in transit. –Message Authentication Codes used to check if encrypted message was altered.

CIT 140: Introduction to ITSlide #18 UNIX Files /var/mail/username /var/spool/mail/username –A user’s messages. /var/spool/mqueue –Messages queued for sending to other hosts. /etc/mail –Mail server (MTA) configuration files. /etc/mail/aliases –MTA mailing lists.

CIT 140: Introduction to ITSlide #19 Features

CIT 140: Introduction to ITSlide #20 The UNIX mail Command Options for sending with the mail command -s A subject: line is included in the message header for all recipients -c A carbon copy is sent to address add -b A blind carbon copy is sent to address add -h A screen display of message headers is shown first -p All messages are displayed with full headers

CIT 140: Introduction to ITSlide #21 Graphical with KMail

CIT 140: Introduction to ITSlide #22 Graphical with KMail

CIT 140: Introduction to ITSlide #23 Graphical with KMail

CIT 140: Introduction to ITSlide #24 Graphical with KMail

CIT 140: Introduction to ITSlide #25 Graphical with KMail

CIT 140: Introduction to ITSlide #26 pine

CIT 140: Introduction to ITSlide #27 Composing with pine

CIT 140: Introduction to ITSlide #28 Using the pine Address Book