Article ID: 224817 - View products that this article applies to.
This article was previously published under Q224817
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This article presents some basics on Transport Neutral Encapsulation Format (TNEF).
Transport Neutral Encapsulation Format (TNEF) is a Microsoft proprietary method for encoding Rich Text Format (RTF) messages sent across the Internet. A TNEF-encoded message contains a plain text version of the message, an attachment that contains the RTF version, and any OLE objects such as pictures or other attachments that were sent with the message. Some e-mail clients do not understand TNEF encoding, and so it should only be used if you are certain the message will be received by someone using Windows Messaging, Microsoft Exchange Client, or Outlook.
When a message containing TNEF information is received by a mail client that does not understand TNEF, an attachment is created with the name Winmail.dat. In some cases, the mail server will look for and strip out the TNEF and Winmail.dat information.
There are servers that can be configured to look for TNEF and winmail.dat and strip it out, but the usual symptom in that case is that the servers completely remove the Winmail.dat attachment.
For additional information about Winmail.dat, please see the following article in the Microsoft Knowledge Base:
197064NOTE: The information in the article mentioned, applies if the sender is using Outlook in Corporate/Workgroup (CW) mode. The Internet Mail Only (IMO) mode works quite differently with regards to TNEF.
(https://support.microsoft.com/kb/197064/EN-US/ )OL2000: (CW) Winmail.dat Attachments Included in Messages
For additional information about Transport Neutral Encapsulation Format, please see the following articles in the Microsoft Knowledge Base:
(https://support.microsoft.com/kb/197066/EN-US/ )OL2000: Attachments Sent with TNEF Not Visible to Some Recipients
(https://support.microsoft.com/kb/197540/EN-US/ )OL2000: (CW) Accept, Decline, Tentative Not on Meeting Request
(https://support.microsoft.com/kb/197635/EN-US/ )OL2000: (IMO) TNEF Information Not Retained Sending HTML E-mail
(https://support.microsoft.com/kb/217390/EN-US/ )OL2000: (CW) Rich Text Signed Messages Are Always Sent as HTML