TNEF's Enough for macOS Providing a free "winmail.dat" solution to the Mac community for over 18 years! TNEF's Enough allows Macs to read and extract files from Microsoft TNEF stream files. The files are usually received by SMTP based e-mail programs from Microsoft Exchange and Microsoft Outlook users. The SMTP based e-mail program will usually receive either a MIME attachment named "winmail.dat"