TNEF

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please really discuss and incorporate changes instead of overwriting everything. - Jabo ( discussion ) 18:15, 25 Mar. 2013 (CET)

Transport Neutral Encapsulation Format ( TNEF ) is the name of a proprietary file implemented by Microsoft in their e-mail program Microsoft Outlook and in Exchange - format for file attachments in e-mails. It contains both “descriptive structures” and the actual attachment, embedded in the email . File attachments in this format are often automatically given the file name winmail.dat or win.dat .

Quirks and problems

Since it is a proprietary format, perhaps the most obvious problem is that a receiving e-mail program does not understand the format. Nowadays (as of 2017) most programs are able to process these types of attachments. B. not everyone always has the latest versions. However, especially in the automatic processing of e-mails, the probability of problems is higher. Since mostly no end-user applications but modules for the respective programming languages ​​are used here, it often happens that "unpacking" TNEF attachments is simply overlooked.

It can happen that someone sends or forwards such an attachment again as a file with another mail program (possibly with a different file name than the standard name winmail.dat ), so that the recipient does not necessarily initially recognize that it is such a format acts.

Above all, it is problematic that “descriptive structures” actually do not belong in the element that they describe. There are already clearly defined structures for the elements that can (should) occur within e-mails , in order to avoid the effect that certain proprietary software is needed to access the content of the e-mail or attached files.

solutions

Depending on the e-mail program used, you cannot solve problems with this type of attachment yourself, but rely on the sender who uses Outlook to change the settings of his send format. Without using Outlook yourself, the following procedure is recommended:

• For yourself (on the recipient side):
  • If you can split off and save a file with the name winmail.dat with the e-mail program you use yourself , you can use third-party software to convert the split attachment (there are auxiliary programs for various operating systems and e-mail programs to convert such files to extract and save in a readable format ; usually called Winmail Opener or similar).
  • If this is not possible (and the e-mail does not contain a usable winmail.dat attachment), an attempt can be made to use another e-mail program that displays the attachment as winmail.dat . (NB: it is possible that an e-mail program shows a winmail.dat attachment, but the size and content of the attachment does not correspond to the sent one.)
• From the sender:
  • If a solution on the recipient's side does not work, one is forced to ask the sender to deactivate the use of TNEF in Outlook and to resend the e-mail (the instructions for this are described in the article in the "Microsoft Knowledge Base" linked below ).

See also

• Multipurpose Internet Mail Extensions (MIME)
• Internet Media Type
• Header (email)

Web links

• Microsoft Support:
  • https://support.microsoft.com/kb/290809/de
  • Microsoft Knowledge Base - Description of Transport Neutral Encapsulation Format
  • Deactivation
  • Fixed issues with deactivating TNEF in Outlook 2007 to 2010

• Online unpacker for winmail.dat / ATT0001.dat e-mail attachments: winmaildat.com
• Converter & unpacker for Thunderbird : LookOut or the serviced successor LookOut (fix version)

Individual evidence

1. ↑ Instructions for solving the problem in the Microsoft knowledgebase.
2. ↑ Instructions for solving the problem in the Microsoft knowledgebase for Outlook 2007 & 2010.