Apresentação realizada no dia 25/10/2013, sobre os protocolos de e-mail, na disciplina de Redes e Sistemas Distribuídos no Centro Universitário Católica de Santa Catarina.

1. Protocolos de E-mail
Diogo Rodrigues Lopes
Paulo Vitor Bischof

2. Agenda
1.
2.
3.
4.
5.
Introdução;
História;
Funcionamento;
Protocolos Seguros;
Considerações finais;

3. SMTP
• Protocolo padrão de envio de E-mail
• Criado em 1982, na Universidade do Sul da
Califórnia por Jon Postel
• Envia o e-mail do client para o server

4. SMTP Syntax
COMMAND
HELO <domain>
MAIL FROM:<reversepath>
RCPT TO:<forwardpath>
DATA
RSET
VRFY <string>
EXPN <string>
HELP [<string>]
NOOP [<string>]
QUIT
DESCRIPTION
(Hello) Connect to the server as specified in <domain>
Tell the server the sender’s identity as specified in <reversepath> [Mail-parameters]
(Recipient) Tell the server the intended recipient’s identity as
specified in [Rcpt-parameters] <forward-path>
Convey the message body to the server
(Reset) Reset the server connection
(Verify) Ask the receiver to confirm that a user has been
identified
(Expand) Ask the receiver to confirm that a mailing list has
been identified
Obtain help information
(No operation) Indicate no operation, but signify the sender is
still connected (i.e.,“alive”)
Close the server connection

5. POP
•
•
•
•
Criado em 1984
Protocolo de leitura
Copia as mensagens do server para o client
Possui problemas de sincronização, pois foi
projetado para deletar as mensagens do
servidor

6. POP
COMMAND
BASIC COMMANDS FROM RFC 918
USER <name>
PASS <password>
STAT
LIST [msg]
RETR <msg>
DELE <msg>
QUIT
NOOP
RSET
DESCRIPTION
Set username
Set password
Check the status of the mailbox, typically retrieves
number of messages
List messages in the mailbox; Optional argument for
message [msg]
Retrieve message <msg>
Delete message <msg>
Quit
No operation
Reset

7. POP
COMMAND
OPTIONAL COMMANDS FROM RFC 1939
TOP <msg> <n>
UIDL [msg]
APOP <name> <digest>
EXTENSION COMMAND FROM RFC 2449
CAPA
DESCRIPTION
Retrieve the top <n> lines of message <msg>
Retrieve unique id for [msg]
A more robust form of authentication than
USER/PASS
Retrieve a list of capabilities supported by the
POP3 server

8. IMAP
• Criado em 1988, para solucionar problemas
conhecidos do protocolo POP.
• Possui mais recursos que o POP
• Solucionou a sincronização de E-mail entre
server e clients.
• Permite pesquisar e-mails no servidor

9. IMAP
COMMAND
NOOP
STARTTLS
AUTHENTICATE <type>
LOGIN <user> <passwd>
LOGOUT
SELECT <mailbox>
EXAMINE <mailbox>
CREATE <mailbox>
DELETE <mailbox>
RENAME <mailbox>
<newmailbox>
SUBSCRIBE <mailbox>
UNSUBSCRIBE <mailbox>
DESCRIPTION
Perform no operation
Establish confidentiality and integrity protection
Choose authentication method
Login with username and password
Logout the current user
Select the desired mailbox to access
Same as SELECT except opens mailbox for read-only
Create a mailbox with the name <mailbox>
Delete selected mailbox
Rename mailbox
Subscribe to selected mailbox
Unsubscribe from selected mailbox

10. IMAP
COMMAND
LIST <reference> [pattern]
LSUB <reference> [pattern]
STATUS <mailbox> <item>
APPEND <mailbox> [flags] <msg>
CHECK
CLOSE
EXPUNGE
SEARCH <criteria>
FETCH <message> <item>
STORE <message> <item>
<newvalue>
COPY <message> <mailbox>
UID <command> [args]
CAPABILITY
DESCRIPTION
List contents of current reference based on an optional
pattern
List a set of mailboxes matching the pattern
Show the status of specific items in the selected
mailbox
Append a message to the selected mailbox
Perform a checkpoint on the currently selected mailbox
Close the currently selected mailbox
Expunge deleted messages from the mailbox
Search the mailbox based on certain criteria
Fetch the specified item from the selected message
Update the selected item in a message
Copy a message to the provided mailbox
Perform an operation on a message based on its UID
Query the server for its capabilities

11. Protocolos Seguros
•
•
•
•
Surgiram na década de 90
PGP
SSL
TLS

12. Considerações finais
• Posso usar SSL ou TLS?
• PGP ainda existe?
• Qual protocolo devo configurar no meu
smartphone?
• Se usar SSL a NSA pode ler meu e-mail?

13. Referência bibliográfica
KUROSE, James F. Redes de Computadores e a
Internet – 5ª Edição.
TANENBAUM, Andrew S.; Redes de
Computadores - 5ª Edição. Pearson Education
do Brasil, 2011.

14. Obrigado
Diogo Rodrigues Lopes
Paulo Vitor Bischof