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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-2E253B30-2611-546D-AE5B-1752556FC8E8" xml:lang="en"><title>SMTP |
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13 Concepts</title><prolog><metadata><keywords/></metadata></prolog><conbody> |
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14 <p>This section section describes the Simple Mail Transfer Protocol (SMTP) |
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15 and its implementation on Symbian platform. </p> |
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16 <section id="GUID-DBF1C87D-7360-54B7-8658-B6659BF77F06-GENID-1-8-1-16-1-1-6-1-7-1-4-1-2-2"><title>SMTP protocol</title> <p>SMTP |
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17 is the most widely used protocol for sending emails. It is a text-based and <b>push</b> protocol |
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18 that cannot <b>pull</b> messages from a remote server on demand. </p> <p>One |
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19 or more recipients of a message are specified in a message along with the |
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20 message text and other encoded objects. The message is then transferred to |
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21 a remote server using a procedure of queries and responses between the client |
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22 and server. Either an end-user's email client (Mail User Agent (MUA)) or a |
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23 relaying server's Mail Transport Agents (MTA) can act as an SMTP client. The |
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24 SMTP client initiates a TCP connection to SMTP server on port 25 (unless overridden |
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25 by configuration). </p> <p>SMTP is more suitable for a machine permanently |
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26 connected to the Internet. To retrieve messages only on demand, which is the |
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27 most common requirement on a single-user computer, a mail client must use |
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28 POP3 or IMAP4. POP3 is mostly preferred when single-user computers connected |
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29 to the Internet only intermittently. </p> </section> |
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30 <section><title>Symbian platform implementation of SMTP</title> <p>SMTP is |
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31 a Mail Transfer Agent (MTA) used to transfer emails to a SMTP server which |
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32 then forwards them on to a specified destination. </p> <p>Sending an email |
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33 generally consists of three phases: connect and authorise to server, send |
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34 emails and quit. </p> <p>The SMTP component is responsible for sending email |
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35 messages composed and stored in the Message Server’s Message Store. </p> <ol id="GUID-8FCD7F76-46FD-58E9-9EBA-B178B98F0782"> |
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36 <li id="GUID-A8B5A1FA-DE84-51E8-B2B3-B4FCD073E0D2"><p>The SMTP client initiates |
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37 a connection with the SMTP server. Depending on the user’s email settings, |
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38 this may have been initiated over a secure SSL/TLS socket on port 465. </p> </li> |
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39 <li id="GUID-F18E9E52-DF7A-5127-B6DD-FB08663025E0"><p>Depending on how the |
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40 user has configured the email settings and the capabilities of the SMTP server, |
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41 SMTP authentication may also be required. </p> </li> |
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42 <li id="GUID-74561ABB-4B7A-58E7-B79D-5473C3149476"><p>Mail <b>From</b> and |
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43 recipient <b>To</b> are sent. </p> </li> |
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44 <li id="GUID-7ABADE92-CAF1-524A-A8AB-288E9849BED1"><p>The message header fields |
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45 for the email message stored in the Message Store are then transmitted, each |
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46 one separated by a CRLF. </p> </li> |
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47 <li id="GUID-7932B3D6-270F-5983-8521-8AC83C7AA450"><p>The last CRLF is sent |
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48 to indicate the end of the RFC 2822 header. </p> </li> |
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49 <li id="GUID-2A05FF85-4E42-5EEE-A2C5-4763C887E3D2"><p>The message body and |
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50 encoded attachments are sent. </p> <p>The encoding format (uuencode or MIME, |
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51 character sets) depends on the user’s email settings and locale. </p> </li> |
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52 <li id="GUID-7040A4EB-AA7C-5932-B7FF-89595D9256D0"><p>Finally, the body is |
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53 terminated by a CRLF. </p> <p>CRLF sequence, and the email is queued by the |
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54 SMTP server for sending. </p> </li> |
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55 </ol> </section> |
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56 <section><title>SMTP example</title> <p>For more details on implementing the |
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57 IMAP4 MTM functions, see <xref href="GUID-D73AD200-BE4D-50BF-BCF9-14627DE530B7.dita">example |
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58 code</xref>. </p> </section> |
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59 </conbody><related-links> |
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60 <link href="GUID-4F703F85-080F-5B77-B94D-5449764828F3.dita"><linktext>SMTP MTM</linktext> |
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61 </link> |
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62 </related-links></concept> |