Editing Transport Neutral Encapsulation Format

{{Short description|Proprietary email attachment format}}
{{Use American English|date=December 2017}}
{{Use mdy dates|date=December 2017}}
'''Transport Neutral Encapsulation Format''' or '''TNEF''' is a proprietary [[email]] attachment format used by [[Microsoft Outlook]] and [[Microsoft Exchange Server]]. An attached [[computer file|file]] with TNEF encoding is most often named ''winmail.dat'' or ''win.dat'', and has a MIME type of ''Application/MS-TNEF''.
The official ([[Internet Assigned Numbers Authority|IANA]]) media type, however, is ''application/vnd.ms-tnef''.<ref name="iana">{{cite web|title=Some Microsoft Media Types for registration
|url=https://www.iana.org/assignments/media-types/application/vnd.ms-tnef|publisher=IANA|access-date=October 25, 2010}}</ref>

== Overview ==
Some TNEF files contain information used only by Outlook to generate a richly formatted view of the message, such as embedded ([[Object Linking and Embedding|OLE]]) documents or Outlook-specific features such as forms, voting buttons, and meeting requests. Other TNEF files may contain files which have been attached to an e-mail message.

Within the Outlook [[e-mail client]], TNEF encoding cannot be explicitly enabled or disabled (except via a registry setting<ref name="KB958012">{{cite web|title=When you use Outlook 2007 to send an e-mail message, the recipient of the message sees an attachment that is called Winmail.dat|url=http://support.microsoft.com/kb/958012|publisher=Microsoft|date=July 29, 2009|access-date=March 3, 2011}}</ref>). Selecting [[Rich Text Format|RTF]] as the format for sending an e-mail implicitly enables TNEF encoding, using it instead of the more common and widely compatible [[MIME]] standard. When sending [[plain text]] or [[HTML]] format messages, some versions of Outlook (apparently including '''Outlook 2000'''<ref name="outlook2000"/>) prefer MIME, but may still use TNEF under some circumstances (for example, if an Outlook feature requires it).<ref name="outlook2000">{{cite web|title=Description of Transport Neutral Encapsulation Format (TNEF) in Outlook 2000|url=http://support.microsoft.com/kb/241538|publisher=Microsoft|access-date=September 11, 2009|archive-date=September 4, 2009|archive-url=https://web.archive.org/web/20090904213017/http://support.microsoft.com/kb/241538|url-status=dead}}</ref><ref name="outlook2003">{{cite web|title=How e-mail message formats affect Internet e-mails in Outlook|url=http://support.microsoft.com/kb/290809|publisher=Microsoft|date=2005-03-30|access-date=October 13, 2006}}</ref>

TNEF attachments can contain security-[[sensitive information]] such as user login name and file paths,<ref name="outlook2000"/><ref name="outlook2003"/> from which access controls could possibly be inferred.

== Exchange Server ==
{{Unreferenced section|date=April 2010}}
Native-mode Microsoft Exchange 2000 organizations will, in some circumstances, send entire messages as TNEF-encoded raw binary independent of what is advertised by the receiving [[SMTP]] server. As documented in Microsoft KBA #323483,<ref>{{Cite web|url=http://support.microsoft.com/kb/323483|title=Microsoft KBA #323483}}</ref> this technique is not [[Request for Comments|RFC]]-compliant because these messages have the following characteristics:
* They may include non-ASCII characters outside the 0–127 US-ASCII range.
* The lines in these messages are often too long for transport via SMTP.
* They do not follow the CRLF.CRLF message termination semantics as specified in RFC 821.

Internal communications between Exchange Servers (2000 and later) over SMTP encode the message in S/TNEF (Summary TNEF) format. The conversion between the format needed by the end client on the Internet is performed on the last Hub Transport server before final delivery, and when the Hub Transport role of an Exchange Server is about to deliver the message to a mailbox role server, the message is converted to [[MAPI]] format for storage.

S/TNEF differs from TNEF in that it is 8-bit (not 7-bit for TNEF) and does not contain a plain-text portion.

==Decoding==
Programs to decode and extract files from TNEF-encoded attachments are available on many platforms.

===Multiplatform===
* [[Geary (email client)]] supports TNEF since version 3.33.1
* TNEF Parse – [[Claws Mail]] plugin<ref>{{cite web|url=http://www.claws-mail.org/plugins.php|title=Claws Mail - Plugins|website=www.Claws-Mail.org|access-date=December 23, 2017}}</ref>
* LookOut<ref>{{cite web|url=https://addons.mozilla.org/en-US/thunderbird/addon/lookout/|title=LookOut|website=addons.Mozilla.org|date=September 30, 2011 |access-date=December 23, 2017}}</ref> or its successor LookOut (fix version)<ref>{{cite web|url=https://addons.mozilla.org/en-US/thunderbird/addon/lookout-fix-version/|title=LookOut (fix version)|website=addons.Mozilla.org|access-date=December 23, 2017}}</ref> – [[Mozilla Thunderbird]] extension. See also:
** LookOut project page at MozDev.org<ref>{{cite web|url=http://lookout.mozdev.org/|title=mozdev.org - lookout: index|website=lookout.MozDev.org|access-date=December 23, 2017|archive-date=December 24, 2017|archive-url=https://web.archive.org/web/20171224213807/http://lookout.mozdev.org/|url-status=dead}}</ref>
** Bug 77811 – Inline viewer for Microsoft proprietary mail formats, a 21-plus-year-old bug report at the Mozilla [[Bugzilla]]<ref>{{cite web|url=https://bugzilla.mozilla.org/show_bug.cgi?id=77811|title=77811 - Inline viewer for Microsoft proprietary mail formats (ms-tnef, etc.) ["winmail.dat"]|website=bugzilla.Mozilla.org|access-date=December 23, 2017}}</ref>
* [[Wireshark]] – Version 1.2 and later can open and dissect winmail.dat files, although it is not useful as a mail reader
* KTNEF – LGPL TNEF extractor by [[KDE]]<ref>{{cite web|url=https://invent.kde.org/pim/ktnef/|title=KTnef|website=KDE Gitlab}}</ref>

===Unix-like or POSIX command-line===
* yTNEF – [[GNU General Public License|GPL]] TNEF extractor from the [[POSIX]] command-line, designed specifically for reading winmail.dat<ref name="ytnef">{{cite web|url=https://github.com/Yeraze/ytnef|title=ytnef: Yeraze's TNEF Stream Reader - for winmail.dat files|last=Yeraze|date=November 21, 2017|access-date=December 23, 2017|via=GitHub}}</ref>
* TNEF – GPL TNEF extractor from the POSIX command-line<ref>{{cite web|url=https://github.com/verdammelt/tnef|title=tnef|first=Mark|last=Simpson|date=December 8, 2017|access-date=December 23, 2017|via=GitHub}}</ref>

===Mac===
* Klammer – Shareware for [[Mac OS X]], available on App store; also supports MSG files<ref>{{cite web|url=https://itunes.apple.com/us/app/klammer-open-msg-winmail.dat/id436780099?mt=12|archive-url=https://web.archive.org/web/20121113135743/https://itunes.apple.com/us/app/klammer-open-msg-winmail.dat/id436780099?mt=12|url-status=dead|archive-date=November 13, 2012|title=Klammer on the Mac App Store|website=Mac App Store|access-date=December 23, 2017}}</ref>
* MailRaider Pro - Application for Mac OS X, available on App store; also supports MSG files<ref>{{cite web|url=https://itunes.apple.com/us/app/mailraider-pro/id765096886?mt=12|archive-url=https://web.archive.org/web/20140922153306/https://itunes.apple.com/us/app/mailraider-pro/id765096886?mt=12|url-status=dead|archive-date=September 22, 2014|title=MailRaider Pro on the Mac App Store|website=Mac App Store|access-date=December 23, 2017}}</ref>
* Winmail Viewer – Shareware Winmail.dat viewer for Mac OS X 10.6 or later, available on App Store, support open [[Microsoft Outlook]] (1997, 2000, 2003, 2007, 2010). Winmail.dat files, can extract and save Winmail.dat attachments<ref>{{cite web|url=https://apps.apple.com/us/app/winmail-viewer/id682272488?mt=12|title=Winmail Viewer - Open and Read Winmail.dat Files on the Mac App Store|website=Mac App Store|access-date=December 23, 2017}}</ref>
* TNEF's Enough – Freeware decoder for [[Mac OS 9]] and Mac OS X<ref>{{cite web|url=http://www.joshjacob.com/mac-development/tnef.php|title=Josh Jacob - TNEF's Enough|website=www.JoshJacob.com|access-date=December 23, 2017}}</ref>
* tnefDD – Free GPL decoder with drag-and-drop functionality for Mac OS X<ref>{{cite web|url=http://tnefDD.sourceforge.net|title=tnefDD|website=SourceForge.net|access-date=December 23, 2017}}</ref>
* TNEF – [[MacPorts]] version of the TNEF command-line decoder Mac OS X<ref>{{cite web|url=http://www.macports.org/ports.php?by=name&substr=tnef|title=The MacPorts Project -- Available Ports|first=Jim Mock|last=(mij@macports.org)|website=www.MacPorts.org|access-date=December 23, 2017}}</ref>
* Letter Opener (''previously known as OMiC'') – Shareware, plugin for [[Apple Mail]]<ref>{{cite web|url=http://www.restoroot.org/OMiC|title=Letter Opener|website=Restoroot.org|access-date=December 23, 2017|url-status=dead|archiveurl=https://web.archive.org/web/20061102080739/http://www.restoroot.org/OMiC/|archivedate=November 2, 2006|df=mdy-all}}</ref>

===iPhone and iPad===
* Winmail File Viewer – Paid universal app for the [[iPhone]], [[iPod Touch]] and [[iPad]] to open winmail.dat attachments with option to save and share extracted files<ref>{{cite web|url=https://apps.apple.com/app/winmail-file-viewer/id379500151|title=Winmail File Viewer on the App Store|website=App Store|access-date=January 8, 2018}}</ref>
* WinMail.dat Viewer - Browse Outlook winmail.dat files – Paid universal app for the [[iPhone]], [[iPod Touch]] and [[iPad]] to open winmail.dat attachments with option to view, save and share extracted files<ref>{{cite web|url=https://itunes.apple.com/us/app/winmail.dat-viewer-browse/id531284520?mt=8|archive-url=https://web.archive.org/web/20160316051023/https://itunes.apple.com/us/app/winmail.dat-viewer-browse/id531284520?mt=8|url-status=dead|archive-date=March 16, 2016|title=WinMail.dat Viewer for OS 10 on the App Store|website=App Store|date=July 11, 2017 |access-date=January 8, 2018}}</ref>
* Winmail File Viewer+ – Paid universal app for the [[iPhone]], [[iPod Touch]] and [[iPad]] to open winmail.dat attachments with option to save and share extracted files<ref>{{cite web|url=https://itunes.apple.com/app/id545262569|archive-url=https://web.archive.org/web/20160305214915/https://itunes.apple.com/app/id545262569|url-status=dead|archive-date=March 5, 2016|title=Winmail Viewer for iPhone and iPad on the App Store|website=App Store|date=July 12, 2017 |access-date=January 8, 2018}}</ref>
* Klammer - open EML, MSG and Winmail.dat files – Paid universal app for the [[iPhone]], [[iPod Touch]] and [[iPad]] with in-app purchase to provide functionality<ref>{{cite web|url=https://itunes.apple.com/us/app/klammer-open-eml-msg-and-winmail-dat-files/id386777877?mt=8|archive-url=https://web.archive.org/web/20121111075805/https://itunes.apple.com/us/app/klammer-open-eml-msg-and-winmail-dat-files/id386777877?mt=8|url-status=dead|archive-date=November 11, 2012|title=Klammer on the App Store|website=App Store|access-date=January 8, 2018}}</ref>
* WinDat Opener – Paid app for the [[iPhone]], [[iPod Touch]] and [[iPad]]<ref>{{cite web|url=https://apps.apple.com/us/app/windat-opener/id404795709|title=WinDat Opener on the App Store|website=App Store|access-date=January 8, 2018}}</ref>
* Letter Opener – Free Universal app for the [[iPhone]], [[iPod Touch]] and [[iPad]] with in-app purchase to provide functionality<ref>{{cite web|url=https://itunes.apple.com/us/app/letter-opener/id395502240?mt=8|archive-url=https://web.archive.org/web/20121110205030/https://itunes.apple.com/us/app/letter-opener/id395502240?mt=8|url-status=dead|archive-date=November 10, 2012|title=Connecting to the iTunes Store.|website=[[iTunes]]|access-date=January 8, 2018}}</ref>
* TNEF's Enough - Free Universal app for iPhone, iPod Touch, and iPad<ref>{{Cite web|url=https://apps.apple.com/us/app/tnefs-enough/id1059932557|title=TNEF's Enough|website=App Store|date=February 2, 2020 |language=en-us|access-date=2020-03-17}}</ref>

===Microsoft Windows===
* Winmail.dat Reader – Freeware easy-to-use decoder<ref name="winmail-dat.com">{{cite web|url=https://www.winmail-dat.com/|title=Winmail.dat Reader - Open winmail.dat files (Freeware)|website=www.Winmail-dat.com|access-date=December 23, 2017}}</ref>
* Winmail Opener – Freeware decoder<ref>{{cite web|url=https://www.eolsoft.com/freeware/winmail_opener/|title=Winmail Opener - freeware utility for opening winmail.dat and other TNEF-encoded files|website=www.Eolsoft.com|access-date=December 23, 2017}}</ref>
* tnef2win – Freeware decoder<ref>{{cite web|url=https://www.petersen.de/english/tnef2win|title=tnef(TO)win, convert mstnef-attachments|first=Frank|last=Petersen|website=www.Petersen.de|access-date=December 23, 2017}}</ref>
* Free File Viewer – Freeware decoder<ref>{{cite web|url=http://www.freefileviewer.com|title=PDF, DOC, DOCX, DAT, BIN, PHP Viewer - FreeFileViewer|website=www.FreeFileViewer.com|access-date=December 23, 2017}}</ref>
* fentun – Freeware decoder<ref>{{cite web|url=http://www.fentun.com/|title=Welcome to Fentun's Home Page|website=www.Fentun.com|access-date=December 23, 2017|archive-date=November 26, 2004|archive-url=https://web.archive.org/web/20041126072804/http://www.fentun.com/|url-status=dead}}</ref>
* Winmail.dat Viewer – modern Windows 8 app (non-free)<ref>{{cite web|url=http://apps.microsoft.com/windows/en-US/app/8c40043e-fe17-49eb-98b1-191263f263bf|title=Get Winmail.dat Viewer - Letter Opener - Microsoft Store|website=Microsoft Store|access-date=December 23, 2017}}</ref>

===Android===
* TNEF Extractor – A free and open source (GPLv3) Android app<ref>{{cite web|url=https://gitlab.starapps-network.com/tools/tnef-extractor|title=Tools / TNEF Extractor · GitLab|access-date=June 22, 2020}}</ref>
* Opener – A free Android app<ref>{{cite web|url=https://play.google.com/store/apps/details?id=icab.winmail|title=Winmail.dat Opener|website=Google.com|access-date=December 23, 2017}}</ref>
* Reader - Free Android app also available<ref name="winmail-dat.com"/>

===Online===
* winmail.dat extractor and document converter – Free, in modern, responsive theme<ref>{{cite web|url=https://doc2any.grapph.com|title=Free Online Document Converter|first=Milos Wikarski|last=grapph.com|website=doc2any.Grapph.com|access-date=December 23, 2017}}</ref>
* Reader Online – The online version of the Winmail.dat Reader (free)<ref>{{cite web|url=https://www.winmail-dat.com/online.php|title=Online version - Winmail.dat Reader|website=www.Winmail-dat.com|access-date=December 23, 2017}}</ref>
* tud.at service – Web service and [[GNU General Public License|GPL]] licensed [[PHP]] script for reading attachments in winmail.dat files<ref>{{cite web|url=https://tud.at/php/tnef/index.php|title=MS-TNEF degenerator|website=tud.at|access-date=December 23, 2017}}</ref>
* www.winmaildat.com – Another online winmail.dat extractor which allows to upload up to 5 MB<ref>{{cite web|url=https://www.winmaildat.com|title=www.winmaildat.com|website=Winmaildat.com|access-date=December 23, 2017}}</ref>
* the-computer-site.com – converts winmail.dat file to a zip file<ref>{{cite web|url=https://the-computer-site.com/winmail-dat.php|title=the-computer-site.com - The Computer Site - Extract Attachments from WINMAIL.DAT files|website=The-Computer-Site.com|access-date=December 23, 2017}}</ref>

===Software libraries===
* JTNEF – [[GNU General Public License|GPL]] Java TNEF package<ref>{{cite web|url=http://www.freeutils.net/source/jtnef/|title=JTNEF - Java TNEF package|website=www.FreeUtils.net|access-date=January 8, 2018}}</ref>
* POI-HMEF – Java library of the [[Apache POI]] project<ref>{{cite web|url=http://poi.apache.org/hmef/index.html|title=POI-HMEF - Java API To Access Microsoft Transport Neutral Encoding Files (TNEF)|website=poi.Apache.org|access-date=January 8, 2018|archive-date=January 14, 2018|archive-url=https://web.archive.org/web/20180114215100/http://poi.apache.org/hmef/index.html|url-status=dead}}</ref>
* MVCOM – Commercial COM component to parse TNEF<ref>{{cite web|url=http://www.encryptomatic.com/mvcom/|title=MVCOM - MAPI-Free COM component for Outlook .pst, .msg, .ost.|website=www.Encryptomatic.com|access-date=January 8, 2018}}</ref>
* Convert::TNEF – TNEF library written in [[Perl]]<ref>{{cite web|url=https://metacpan.org/module/Convert::TNEF|title=Convert::TNEF - Perl module to read TNEF files - metacpan.org|website=Metacpan.org|access-date=January 8, 2018}}</ref>
* tnefparse library – TNEF access library written in [[Python (programming language)|Python]], licensed under [[GNU Lesser General Public License|LGPL]]<ref>{{cite web|url=https://github.com/koodaamo/tnefparse|title=tnefparse: a TNEF decoding library written in python, without external dependencies|date=October 18, 2017|access-date=January 8, 2018|via=GitHub}}</ref>
* Aspose Email – Commercial Java and .NET library that can parse and extract TNEF data<ref>{{cite web|url=https://www.aspose.com/products/email|title=Outlook Alternative - Email APIs for .NET Java Android SharePoint Cloud|first=Farrukh|last=Sheikh|website=www.Aspose.com|access-date=January 8, 2018|archive-date=February 27, 2017|archive-url=https://web.archive.org/web/20170227084249/https://www.aspose.com/products/email|url-status=dead}}</ref>
* EAGetMail Component – Commercial .NET and ActiveX library that can parse and extract TNEF data<ref>{{cite web|url=https://www.emailarchitect.net/eagetmail|title=IMAP4 Component, POP3 Component, Email Parser for C#, VB, C++, Delphi - Retrieve Email, Parse Email, Decrypt Email, S/MIME, Parse winmail.dat, TNEF, Parse Outlook Msg, SSL, TLS|website=www.EmailArchitect.net|access-date=January 8, 2018}}</ref>
* node-tnef - NodeJS command line tool/library that can parse and extract TNEF data<ref>{{cite web|url=https://www.npmjs.com/package/node-tnef|title=node-tnef|first=John|last=Murphy|access-date=August 31, 2018}}</ref>
* libytnef – [[GNU General Public License|GPL]] TNEF extractor library written in C<ref name="ytnef"/>
* MimeKit – A .NET MIME creation and parser library with support for TNEF<ref>{{Cite web |title=MimeKit.Tnef Namespace |url=http://www.mimekit.net/docs/html/N_MimeKit_Tnef.htm |access-date=2022-12-22 |website=www.mimekit.net}}</ref>
* TNEF Decoder - A PHP Library to extract TNEF<ref>{{Cite web |title=github.com/QualityUnit/TNEFDecoder |website=[[GitHub]] |url=https://github.com/QualityUnit/TNEFDecoder}}</ref>

==References==
<references />

==External links==
* Specification:
** [http://msdn.microsoft.com/en-us/library/cc425498%28v=exchg.80%29.aspx "M-OXTNEF: Transport Neutral Encapsulation Format (TNEF) Data Algorithm"] - MS-TNEF format specifications
* Microsoft Support:
** [http://support.microsoft.com/kb/290809 "How e-mail message formats affect Internet e-mails in Outlook"] - How to disable TNEF in Outlook 2002 and 2003
** [http://support.microsoft.com/kb/241538 "Description of Transport Neutral Encapsulation Format (TNEF) in Outlook 2000"] - How to disable TNEF in Outlook 2000
** [http://support.microsoft.com/kb/821750 "How to configure Internet e-mail message formats at the user and the domain levels in Exchange Server 2003"] - Includes instructions on disabling TNEF
* Other:
** [http://www.dwheeler.com/essays/microsoft-outlook-tnef.html "Microsoft Outlook MS-TNEF handling (aka Winmail.dat or 'Part 1.2' problem of unopenable email attachments)"]

[[Category:Windows communication and services]]
[[Category:Microsoft Office]]
[[Category:Email]]