Download - Smtp POP3 IMAP protocol notes
![Page 1: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/1.jpg)
TCP/IP Protocol Suite 1
Upon completion you will be able to:
Electronic Mail:Electronic Mail:SMTP, POP, and IMAPSMTP, POP, and IMAP
• Understand four configurations of email architecture• Understand the functions and formats of a user agent• Understand MIME and its capabilities and data types• Understand the functions and commands of an MTA• Understand the function of POP3 and IMAP4
Objectives
![Page 2: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/2.jpg)
SMTP Protocol originated in 1982 (RFC821, Jon Postel) Standard message format (RFC822,2822, D.
Crocker) Goal: To transfer mail reliably and efficiently
![Page 3: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/3.jpg)
SMTP SMTP clients and
servers have two main components
User Agents – Prepares the message, encloses it in an envelope. (ex. Thunderbird, Eudora)
Mail Transfer Agent – Transfers the mail across the internet (ex. Sendmail, Exim)
Analogous to the postal system in many ways
![Page 4: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/4.jpg)
SMTP SMTP also allows
the use of Relays allowing other MTAs to relay the mail
Mail Gateways are used to relay mail prepared by a protocol other than SMTP and convert it to SMTP
![Page 5: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/5.jpg)
Limitations in SMTP
Only uses NVT 7 bit ASCII format How to represent other data types?
No authentication mechanisms Messages are sent un-encrypted Susceptible to misuse (Spamming,
faking sender address)
![Page 6: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/6.jpg)
TCP/IP Protocol Suite 6
20.1 ARCHITECTURE
To explain the architecture of email, we give four scenarios. We begin To explain the architecture of email, we give four scenarios. We begin with the simplest situation and add complexity as we proceed. The fourth with the simplest situation and add complexity as we proceed. The fourth scenario is the most common in the exchange of email.scenario is the most common in the exchange of email.
The topics discussed in this section include:The topics discussed in this section include:
First Scenario First Scenario Second Scenario Second Scenario Third Scenario Third Scenario Fourth Scenario Fourth Scenario
![Page 7: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/7.jpg)
TCP/IP Protocol Suite 7
Figure 1 First scenario
![Page 8: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/8.jpg)
TCP/IP Protocol Suite 8
When the sender and the receiver of an email are on the same system, we
need only two user agents.
Note:Note:
![Page 9: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/9.jpg)
TCP/IP Protocol Suite 9
Figure 2 Second scenario
![Page 10: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/10.jpg)
TCP/IP Protocol Suite 10
When the sender and the receiver of an email are on different systems, we
need two UAs and a pair of MTAs (client and server).
Note:Note:
![Page 11: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/11.jpg)
TCP/IP Protocol Suite 11
Figure 20.3 Third scenario
![Page 12: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/12.jpg)
TCP/IP Protocol Suite 12
When the sender is connected to the mail server via a LAN or a WAN, we need two UAs and two pairs of MTAs
(client and server).
Note:Note:
![Page 13: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/13.jpg)
TCP/IP Protocol Suite 13
Figure 4 Fourth scenario
![Page 14: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/14.jpg)
TCP/IP Protocol Suite 14
Figure 20.5 Push vs. pull
![Page 15: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/15.jpg)
TCP/IP Protocol Suite 15
When both sender and receiver are connected to the mail server via a LAN or a WAN, we need two UAs, two pairs
of MTAs (client and server), and a pair of MAAs (client and server). This
is the most common situation today.
Note:Note:
![Page 16: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/16.jpg)
TCP/IP Protocol Suite 16
2 USER AGENT
The user agent (UA) provides service to the user to make the process of The user agent (UA) provides service to the user to make the process of sending and receiving a message easier.sending and receiving a message easier.
The topics discussed in this section include:The topics discussed in this section include:
Services Provided by a User Agent Services Provided by a User Agent User Agent Types User Agent Types Sending Mail Sending Mail Receiving Mail Receiving Mail Addresses Addresses Mailing List Mailing List MIME MIME
![Page 17: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/17.jpg)
TCP/IP Protocol Suite 17
Figure 6 User agent
![Page 18: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/18.jpg)
TCP/IP Protocol Suite 18
Some examples of command-driven user agents are mail, pine, and elm
Note:Note:
![Page 19: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/19.jpg)
TCP/IP Protocol Suite 19
Some examples of GUI-based user agents are Eudora, Outlook, and
Netscape.
Note:Note:
![Page 20: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/20.jpg)
TCP/IP Protocol Suite 20
Figure 7 Format of an email
![Page 21: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/21.jpg)
TCP/IP Protocol Suite 21
Figure 8 Email address
![Page 22: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/22.jpg)
TCP/IP Protocol Suite 22
Figure 29 MIME
![Page 23: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/23.jpg)
TCP/IP Protocol Suite 23
Table 1 Table 1 Data types and subtypes in MIMEData types and subtypes in MIME
![Page 24: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/24.jpg)
TCP/IP Protocol Suite 24
Table 1 Table 1 Data types and subtypes in MIME (Continued)Data types and subtypes in MIME (Continued)
![Page 25: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/25.jpg)
TCP/IP Protocol Suite 25
Table 2 Table 2 Content-transfer-encodingContent-transfer-encoding
![Page 26: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/26.jpg)
TCP/IP Protocol Suite 26
Figure 11 Base64
![Page 27: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/27.jpg)
TCP/IP Protocol Suite 27
Table 3 Table 3 Base64 encoding tableBase64 encoding table
![Page 28: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/28.jpg)
TCP/IP Protocol Suite 28
Figure 12 Quoted-printable
![Page 29: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/29.jpg)
TCP/IP Protocol Suite 29
3 MESSAGE TRANSFER AGENT: SMTP
The actual mail transfer requires message transfer agents (MTAs). The The actual mail transfer requires message transfer agents (MTAs). The protocol that defines the MTA client and server in the Internet is called protocol that defines the MTA client and server in the Internet is called Simple Mail Transfer Protocol (SMTP).Simple Mail Transfer Protocol (SMTP).
The topics discussed in this section include:The topics discussed in this section include:
Commands and Responses Commands and Responses Mail Transfer Phases Mail Transfer Phases
![Page 30: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/30.jpg)
TCP/IP Protocol Suite 30
Figure 13 SMTP range
![Page 31: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/31.jpg)
TCP/IP Protocol Suite 31
Figure 14 Commands and responses
![Page 32: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/32.jpg)
TCP/IP Protocol Suite 32
Figure 15 Command format
![Page 33: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/33.jpg)
TCP/IP Protocol Suite 33
Table 4 Table 4 CommandsCommands
![Page 34: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/34.jpg)
TCP/IP Protocol Suite 34
Table 5 Table 5 ResponsesResponses
![Page 35: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/35.jpg)
TCP/IP Protocol Suite 35
Table 20.5 Table 20.5 Responses (Continued)Responses (Continued)
![Page 36: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/36.jpg)
TCP/IP Protocol Suite 36
Figure 20.16 Connection establishment
![Page 37: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/37.jpg)
TCP/IP Protocol Suite 37
Figure 17 Message transfer
![Page 38: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/38.jpg)
TCP/IP Protocol Suite 38
Figure 18 Connection termination
![Page 39: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/39.jpg)
TCP/IP Protocol Suite 39
4 MESSAGE ACCESS AGENT: POP AND IMAP
The third stage of mail delivery uses a message access agent; the client The third stage of mail delivery uses a message access agent; the client must pull messages from the server. Currently two message access must pull messages from the server. Currently two message access protocols are available: Post Office Protocol, version 3 (POP3) and protocols are available: Post Office Protocol, version 3 (POP3) and Internet Mail Access Protocol, version 4.Internet Mail Access Protocol, version 4.
The topics discussed in this section include:The topics discussed in this section include:
POP3 POP3 IMAP4 IMAP4
![Page 40: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/40.jpg)
All Messages
POP3:
IMAP:Dr.Amer
Friends
….headers
Whole message
POP vs. IMAP
Internet
Internet
![Page 41: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/41.jpg)
Post Office Protocol v3
Simple Allows the user to obtain a list of
their Emails Users can retrieve their emails Users can either delete or keep the
email on their system Minimizes server resources
![Page 42: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/42.jpg)
TCP/IP Protocol Suite 42
Figure 19 POP3 and IMAP4
![Page 43: Smtp POP3 IMAP protocol notes](https://reader031.vdocuments.site/reader031/viewer/2022020709/545fa8e3b1af9f16598b4d9c/html5/thumbnails/43.jpg)
TCP/IP Protocol Suite 43
Figure 20 POP3