All about TNEF Files

The TNEF file type is primarily associated with Exchange Server.

TNEF	File extension: TNEF
	File type:	email formatting/attachment

What is a TNEF file?

TNEF files mostly belong to Exchange Server by Microsoft. A TNEF file is an email attachment saved in the Transport Neutral Encapsulation Format used by Exchange Server and Outlook email software. Such attachment can include embedded OLE objects, radio/checkbox buttons, appointments, images etc. Apart from saving attachments in TNEF files, Outlook can also save formatting for an email message's body in a TNEF file. TNEF is chosen as the default encoding for Outlook messages when RTF is selected as the format for sending an email. Third-party email clients on mobile and desktop platforms can also read and render email attachments saved in TNEF files.

How do you open TNEF files?

You need a suitable software like Exchange Server to open a TNEF file. Without proper software you will receive a Windows message "How do you want to open this file?" or "Windows cannot open this file" or a similar Mac/iPhone/Android alert. If you cannot open your TNEF file correctly, try to right-click or long-press the file. Then click "Open with" and choose an application. You can also display a TNEF file directly in the browser:. Just drag the file onto this browser window and drop it.

Online TNEF Text Viewer

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Programs that open and convert TNEF files:

Exchange Server by Microsoft
See the previous paragraphs to learn more about the main application. TNEF files are often referred to as Exchange Server miscs because this type of file is primarily created or used by this software.
Outlook (email formatting/attachment) by Microsoft
Outlook is an email, contacts, and calendar management client for desktop and mobile platforms. It uses a TNEF file to save email attachments and email body formatting. This file format is classified as Misc. Related links: Transport Neutral Encapsulation Format

TNEF file format:

To view or edit TNEF files you need to know the file format, because it determines how the data in this file is stored. The initial characters of a file are called signature, sometimes also referred to as "magic bytes". The signature can be used to infer the file format. File extension, signature and file format must match; otherwise errors will occur when the file is opened. So you need a detailed analysis of a file to find out the format and the associated program. Below is our analysis of the TNEF files:

TNEF is rarely used as a file extension and mainly uses a special format. However, the following two file formats are common:

85% of all TNEF files belong to Transport Neutral Encapsulation Format. The files are using the common file format TNEF. TNEF is short for Transport Neutral Encapsulation Format. It is a proprietary email attachment format used by Microsoft Outlook and Microsoft Exchange Server. An attached file with TNEF encoding is most often named winmail.dat. They consist of unreadable binary data. TNEF files can be up to 6 MB in size, but are often around 2 KB - 560 KB. The file type is relatively new. The files contain the following words: IPM.Microsoft Mail.Note. Some examples of file names are noname.tnef or winmail.tnef.

The remaining 15% of all TNEF files are different files with different signatures. If you want to find out what your TNEF file contains, drag and drop it onto this page.

Technical Data for TNEF File Extension

File classification:

Misc

Related files:

dat, noname, pdf, edb, stm

Mime type:

application/ms-tnef, application/vnd.ms-tnef

a tnef email formatting/attachment is a special file format by Microsoft and should only be edited and saved with the appropriate software.

How to solve problems with TNEF files

Associate the TNEF file extension with the correct application.
Update your software that should actually open email formatting/attachments. Because only the current version supports the latest TNEF file format. Search, therefore, e.g. on the Microsoft manufacturer website after an available Exchange Server update.
To make sure that your TNEF file is not corrupted or virus-infected, get the file again and scan it with Google's virustotal.com.
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