.TNEF File Extension

There is only one file type that uses the .TNEF extension:

Transport Neutral Encapsulation Format

Transport Neutral Encapsulation Format
  • Developer Microsoft
  • Popularity
    3.7 (3 votes)
  • Category Misc Files
  • Format N/A

File generated by Microsoft Exchange email programs such as Outlook; appears as an email attachment for email clients that don't recognize Microsoft's proprietary TNEF format; may cause the text "application/ms-tnef" to appear in the email if the email client does not recognize Microsoft Exchange formatting.

NOTE: Transport Neutral Encapsulation Format files with the extension ".tnef" are rare. Instead, unrecognized Exchange messages are usually seen with the filename Winmail.dat (.DAT file).

Software's name License Platforms
Apple Mail Apple Mail Bundled iOSMac
Microsoft Outlook Microsoft Outlook Commercial MacWindows
Microsoft Outlook 365 Microsoft Outlook 365 Free+ Mac

Updated: September 1, 2011

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