WinDat Opener has been the top rated winmail.dat decoder app for compatibility and reliability on the App Store since 2011. WinDat Opener opens the "winmail.dat" email attachments that are sometimes sent by Microsoft email systems. These file are in “TNEF” format, and usually contain attachments such as spreadsheets or presentations embedded within them. WinDat Opener extracts the embedded attachments hidden inside the winmail.dat file, allowing you to preview then right in WinDat Opener, or open them with another app. WinDat Opener is fully macOS Big Sur optimized, and comes in a native Apple Silicon version for blazing fast performance on the latest generation Apple Macs.
There's also a version of WinDat Opener for iOS.
Works with any email client
WinDat Opener isn't linked to any specific email client - just drag-and-drop winmail.dat files from any location.
Decodes any winmail.dat file
WinDat Opener will open any winmail.dat file. International character sets - no problem. Embedded Windows Mail notes - no problem. HTML or RTF formatted messages - no problem.
Extracts all attachments
WinDat Opener extracts any and all attachments. No exceptions.
Preserves attachment dates
Unlike other TNEF decoders, WinDat Opener preserves attachment dates, making it easy to keep track of file versions.
Extracts meeting requests and contact files
WinDat Opener extracts meeting requests and apointments as iCal files, and contacts information as vCard files. Single apointments, recurruring apointments, etc.
WinDat Opener allows files to be opened from within WinDat Opener, allowing the contents to be examined without copying the attachment to a new location.
What are TNEF files?
Microsoft e-mail programs written for Windows, such as Outlook, sometimes send e-mails in the Transport Neutral Encapsulation Format (TNEF). Most other e-mail programs, including Apple Mail and Microsoft Entourage, do not understand TNEF. If your e-mail program doesn't understand TNEF, instead of seeing the e-mail and/or attachment, you may only see an attachment named "winmail.dat" or "Part 1.2" that you cannot open. Also, sometimes you may receive a TNEF attachment with a generic name such as ATT00008.dat or ATT00005.eml instead. While almost all attachments named "winmail.dat" are TNEF, you could receive non-TNEF attachments with names ending ".dat" or ".eml", or which are named or labeled "Part 1.2".
macOS 10.9 or later