What exactly is “winmail.dat”?


Have you ever received a strange looking attachment called “winmail.dat” on your PC or Mac?
I am sure you must have at some time or another; and you must have wondered what exactly this “winmail.dat” file attachment is? 
Well I have explained in detail what a “winmail.dat” file attachment is, in the post below. 

Winmail.dat or Transport Neutral Encapsulation Format or TNEF is, despite the name, a proprietary E-mail attachment format used by Microsoft Outlook and Microsoft Exchange Server. 
An attached file with TNEF encoding is most often named winmail.dat or win.dat, and has a MIME type of Application/MS-TNEF.

Some winmail.dat files only contain information used by Outlook to generate a richly formatted view of the message, such as embedded (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 email-client winmail.dat encoding cannot be explicitly enabled or disabled. Selecting RTF as the format for sending an e-mail implicitly enables winmail.dat encoding, using it in preference to the more common and widely compatible MIME standard. 
When sending plain text or HTML format messages, Outlook prefers MIME, but may still use winmail.dat format under some circumstances (for example, if an Outlook feature requires it).

Winmail.dat attachments can contain security-sensitive information such as user login name and file paths, from which access controls could possibly be inferred.

1 comment:

  1. Hey, I just downloaded Hiren's app to open winmail.date attachments. It was a seamless download and i ran a test on this app by openning an winmail.date attachment and whaalah, it opened the attachment right away.

    Thanks Hiren!!!



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