218 lines
9.9 KiB
XML
218 lines
9.9 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!--
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====================================================================
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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====================================================================
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-->
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<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V1.1//EN" "../dtd/document-v11.dtd">
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<document>
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<header>
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<title>POI-HMEF - Java API To Access Microsoft Transport Neutral Encoding Files (TNEF)</title>
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<subtitle>Overview</subtitle>
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<authors>
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<person name="Nick Burch" email="nick at apache dot org"/>
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</authors>
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</header>
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<body>
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<section>
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<title>Overview</title>
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<p>HMEF is the POI Project's pure Java implementation of the
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TNEF (Transport Neurtral Encoding Format), aka winmail.dat,
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which is used by Outlook and Exchange in some situations.</p>
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<p>Currently, HMEF provides a read-only api for accessing common
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message and attachment attributes, including the message body
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and attachment files. In addition, it's possible to have
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read-only access to all of the underlying TNEF and MAPI
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attributes of the message and attachments.</p>
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<p>HMEF also provides a command line tool for extracting out
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the message body and attachment files from a TNEF (winmail.dat)
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file.</p>
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<note>
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This code currently lives the
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<link href="http://svn.apache.org/viewcvs.cgi/poi/trunk/src/scratchpad/">scratchpad area</link>
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of the POI SVN repository.
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Ensure that you have the scratchpad jar or the scratchpad
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build area in your classpath before experimenting with this code.
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</note>
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<note>
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This code is a new POI feature, and the first release that will
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contain it will be POI 3.8 beta 2. Until then, you will need to
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build your own jars from a <link href="../subversion.html">svn
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checkout</link>.
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</note>
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</section>
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<section>
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<title>Using HMEF to access TNEF (winmail.dat) files</title>
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<section>
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<title>Easy extraction of message body and attachment files</title>
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<p>The class <em>org.apache.poi.hmef.extractor.HMEFContentsExtractor</em>
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provides both command line and Java extraction. It allows the
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saving of the message body (an RTF file), and all of the
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attachment files, to a single directory as specified.</p>
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<p>From the command line, simply call the class specifying the
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TNEF file to extract, and the directory to place the extracted
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files into, eg:</p>
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<source>
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java -classpath poi-3.8-FINAL.jar:poi-scratchpad-3.8-FINAL.jar org.apache.poi.hmef.extractor.HMEFContentsExtractor winmail.dat /tmp/extracted/
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</source>
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<p>From Java, there are two method calls on the class, one to
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extract the message body RTF to a file, and the other to extract
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all the attachments to a directory. A typical use would be:</p>
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<source>
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public void extract(String winmailFilename, String directoryName) throws Exception {
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HMEFContentsExtractor ext = new HMEFContentsExtractor(new File(winmailFilename));
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File dir = new File(directoryName);
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File rtf = new File(dir, "message.rtf");
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if(! dir.exists()) {
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throw new FileNotFoundException("Output directory " + dir.getName() + " not found");
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}
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System.out.println("Extracting...");
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ext.extractMessageBody(rtf);
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ext.extractAttachments(dir);
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System.out.println("Extraction completed");
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}
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</source>
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</section>
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<section>
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<title>Attachment attributes and contents</title>
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<p>To get at your attachments, simply call the
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<em>getAttachments()</em> method on a <em>HMEFMessage</em>
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instance, and you'll receive a list of all the attachments.</p>
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<p>When you have a <em>org.apache.poi.hmef.Attachment</em> object,
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there are several helper methods available. These will all
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return the value of the appropriate underlying attachment
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attributes, or null if for some reason the attribute isn't
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present in your file.</p>
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<ul>
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<li><em>getFilename()</em> - returns the name of the attachment
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file, possibly in 8.3 format</li>
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<li><em>getLongFilename()</em> - returns the full name of the
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attachment file</li>
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<li><em>getExtension()</em> - returns the extension of the
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attachment file, including the "."</li>
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<li><em>getModifiedDate()</em> - returns the date that the
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attachment file was last edited on</li>
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<li><em>getContents()</em> - returns a byte array of the contents
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of the attached file</li>
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<li><em>getRenderedMetaFile()</em> - returns a byte array of
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a windows meta file representation of the attached file</li>
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</ul>
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</section>
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<section>
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<title>Message attributes and message body</title>
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<p>A <em>org.apache.poi.hmef.HMEFMessage</em> instance is created
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from an <em>InputStream</em> of the underlying TNEF (winmail.dat)
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file.</p>
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<p>From a <em>HMEFMessage</em>, there are three main methods of
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interest to call:</p>
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<ul>
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<li><em>getBody()</em> - returns a String containing the RTF
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contents of the message body.
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<em>Note - see limitations</em></li>
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<li><em>getSubject()</em> - returns the message subject</li>
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<li><em>getAttachments()</em> - returns the list of
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<em>Attachment</em> objects for the message</li>
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</ul>
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</section>
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<section>
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<title>Low level attribute access</title>
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<p>Both Messages and Attachments contain two kinds of attributes.
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These are <em>TNEFAttribute</em> and <em>MAPIAttribute</em>.</p>
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<p>TNEFAttribute is specific to TNEF files in terms of the
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available types and properties. In general, Attachments have a
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few more useful ones of these then Messages.</p>
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<p>MAPIAttributes hold standard MAPI properties and values, and
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work in a similar way to <link href="../hsmf/">HSMF
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(Outlook)</link> does. There are typically many of these on both
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Messages and Attachments. <em>Note - see limitations</em></p>
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<p>Both <em>HMEFMessage</em> and <em>Attachment</em> supports
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support two different ways of getting to attributes of interest.
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Firstly, they support list getters, to return all attributes
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(either TNEF or MAPI). Secondly, they support specific getters by
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TNEF or MAPI property.</p>
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<source>
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HMEFMessage msg = new HMEFMessage(new FileInputStream(file));
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for(TNEFAttribute attr : msg.getMessageAttributes) {
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System.out.println("TNEF : " + attr);
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}
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for(MAPIAttribute attr : msg.getMessageMAPIAttributes) {
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System.out.println("MAPI : " + attr);
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}
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System.out.println("Subject is " + msg.getMessageMAPIAttribute(MAPIProperty.CONVERSATION_TOPIC));
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for(Attachment attach : msg.getAttachments()) {
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for(TNEFAttribute attr : attach.getAttributes) {
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System.out.println("A.TNEF : " + attr);
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}
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for(MAPIAttribute attr : attach.getMAPIAttributes) {
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System.out.println("A.MAPI : " + attr);
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}
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System.out.println("Filename is " + attach.getAttribute(TNEFProperty.CID_ATTACHTITLE));
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System.out.println("Extension is " + attach.getMAPIAttribute(MAPIProperty.ATTACH_EXTENSION));
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}
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</source>
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</section>
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</section>
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<section>
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<title>Investigating a TNEF file</title>
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<p>To get a feel for the contents of a file, and to track down
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where data of interest is stored, HMEF comes with
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<link href="http://svn.apache.org/repos/asf/poi/trunk/src/scratchpad/src/org/apache/poi/hmef/dev/">HMEFDumper</link>
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to print out the contents of the file.</p>
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</section>
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<section>
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<title>Limitations</title>
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<p>HMEF is currently a work-in-progress, and not everything
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works yet. The current limitations are:</p>
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<ul>
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<li>Compressed RTF Message Bodies are not correctly
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decompressed. This means that a call to
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<em>HMEFMessage.getBody()</em> is unlikely to return the
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correct RTF.</li>
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<li>Non-standard MAPI properties from the range 0x8000 to 0x8fff
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may not be being quite correctly turned into attributes.
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The values show up, but the name and type may not always
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be correct.</li>
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<li>All testing so far has been performed on a small number of
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English documents. We think we're correctly turning bytes into
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Java unicode strings, but we need a few non-English sample
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files in the test suite to verify this!</li>
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</ul>
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</section>
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</body>
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</document>
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