POP3

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POP3
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POP3

• Stands for Post Office Protocol Version 3
• RFC in 1993
• POP3 is intended to permit a workstation to
  dynamically access a maildrop on a server host in
  a useful fashion. Usually, this means that the
  POP3 protocol is used to allow a workstation to
  retrieve mail that the server is holding for it.

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POP3

• Doesnt provide extensive mail operations on the
  server
• Normally mail is downloaded, then deleted
• Deletion doesnt really occur until QUIT
• Uses port 110

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Minimal POP3 Commands

• USER name users name
• PASS string users password
• QUIT quits, and updates the mailbox
• STAT status
• LIST msg lists the mail messages (s only)
• RETR msg retrieves a mail message
• DELE msg deletes a message
• NOOP No operation
• RSET resets the mail to its original state

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Example POP3 Transaction
Server
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Establish the Socket
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Server is OK
OK POP3 server ready
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Establish the Socket
USER bob
Primary Thread
Primary Thread
Socket (101)
Client
Server
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This user is OK
OK
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Send the Password
PASS ITSD4304
Primary Thread
Primary Thread
Socket (101)
Client
Server
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The Password is OK
OK
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Ask how the Server is Feeling
STAT
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Im Fine, Thanks!
OK 2 320
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Got Any Mail?
LIST
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Yup
OK 2 messages (320 octets)
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Message One
1 120
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Message Two
2 200
Primary Thread
Primary Thread
Socket (101)
Client
Server
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End
.
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Get Message One
RETR 1
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Message One Coming!
OK 120 octets
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Message One Coming!
ltthe POP3 server sends message 1gt
Primary Thread
Primary Thread
Socket (101)
Client
Server
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End of Message 1
.
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Get Message One
DELE 1
Primary Thread
Primary Thread
Socket (101)
Client
Server
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Message 1 Gone!
OK message 1 deleted
Primary Thread
Primary Thread
Socket (101)
Client
Server
Note its not really gone
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Get Message One
QUIT
Primary Thread
Primary Thread
Socket (101)
Client
Server
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QUIT Commits/Updates
OK bob POP3 server signing off
Primary Thread
Primary Thread
Socket (101)
Client
Server
Note now its gone
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Socket Disposed
Primary Thread
Primary Thread
Client
Server
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