A message I've received through the POP3Client has an attachment of type application/ms-tnef with no filename, what is it?


	ID: S2E20 DATE: 
		N/A

Mime Type application/ms-tnef is a Microsoft proprietary file type for encapsulating formatting information and objects in an email message. Microsoft advise that ms-tnef should only be used when both the sender and recipient are using Windows Messaging, Microsoft Exchange Client, or Outlook - it is not suitable for emails which will be received by non-Microsoft products.

In most cases the ms-tnef data will include only formatting information and can be safely ignored -indeed many mail servers can be configured to automatically remove ms-tnef sections.

If the message containing the ms-tnef data is sent in uuencoded format the uuencoded ms-tnef data will have a filename of WINMAIL.DAT. If the message is sent in a MIME compliant format then the data will be in section of type application/ms-tnef with no filename.

In general any attachment which has a mime type of application/ will only make sense to the application for which it is intended. In the case of ms-tnef the application is Outlook, other examples are application/ms-excel and application/ms-word.

Microsoft Knowledge Base Article - 224817 'OL2000: Transport Neutral Encapsulation Format (TNEF) Basics' has some more basic information and links to other articles about ms-tnef.

These third party links also have more information on ms-tnef:

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