EMail

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E-Mail
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Apa dan Bagaimana Email bekerja

• Apa itu email?
• Aplikasi gabungan standar RFC 822 dan MIME
• Bagaimana e-mails bekerja ?
• MUAs dan MTAs
• SMTP, POP3 dan IMAP

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Bagaimana email dikirim?
Internet
MTA
LAN
LAN
MUA
MUA
Recipient
Sender
MTA

• MUA Mail User Agent, aka Mail Client
• MTAMail Transport Agent, aka Mail Server

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Linux MTA Software

• Sendmail
• Paling tua dan paling rawan buffer overflow
• Postfix
• Qmail

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RFC 822

• E-mail adalah pesan yang terdiri atas kumpulan
  string ASCII dalam format RFC 822 (dikembangkan
  thn 1982).
• Terdiri atas dua bagian, yang dipisahkan baris
  kosong
• Header sender, recipient, date, subject,
  delivery path,
• Body isi pesan
• Bagaimana dengan pesan non ascii yang dilekatkan
  pada email, cth attachment

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Contoh Pesan RFC 822

• From fitri_at_eepis-its.edu
• To agustina_at_sai.co.id
• Cc kselmaa_at_hotmail.com
• Subject RFC 822 example
• Date Fri, 15 June 2007 135849
• Contoh RFC822 pesan, berformat ASCII.

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MIME

• MIME Multipurpose Internet Mail Extensions
• Menambah kapabilitas RFC 822 agar e-mail mampu
  membawa content non-ASCII.
• Menambahkan 5 header field pada email untuk
  spesifikasi MIME dan content
• tipe,encoding,id,desc.

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MIME Headers

• MIME-Version (must be 1.0)
• Content-Type
• Content-Transfer-Encoding
• Content-ID - optional
• Content-Description - optional

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POP dan IMAP

• POP ?
• From en.wikipedia.org
• The design of POP3 and its procedures supports
  end-users with intermittent connections (such as
  dial-up connections), allowing these users to
  retrieve e-mail when connected and then to view
  and manipulate the retrieved messages without
  needing to stay connected. Although most clients
  have an option to leave mail on server, e-mail
  clients using POP3 generally connect, retrieve
  all messages, store them on the user's PC as new
  messages, delete them from the server, and then
  disconnect
• IMAP ?
• From en.wikipedia.org
• When using POP3, clients typically connect to
  the e-mail server briefly, only as long as it
  takes to download new messages. When using IMAP4,
  clients often stay connected as long as the user
  interface is active and download message content
  on demand. For users with many or large messages,
  this IMAP4 usage pattern can result in faster
  response times.

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Web-based Access

• Contoh at webmail.eepis-its.edu
• Menggunakan username/passwd untuk otentikasi
• Interaksi client-server menggunakan over HTTP
  (atau htpps) bukan POP/IMAP.
• Lebih secure
• Contoh gmail, yahoomail,squirrelmail,dll

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MTA to MUA

• Sistem UNIX mentransfer e-mail dari MTA ke mesin
  user.
• Menggunakan elm, pine, xmail untuk membaca mail
  di mesin user
• Menggunaka username dan password untuk masuk ke
  mailbox user
• Amankah ????

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Simple Mail Transfer Protocol

• Berdasarkan RFC 821 menangani,
• MUA-MTA
• MTA-MTA
• SMTP dibawa lewat Internet dan tidak diproteksi.
• Tanpa otentikasi, mudah sekali menipu asal email
  (walaupun pada mail header biasa dicantumkan
  source IP address).