You may receive winmail.dat files from the senders who are using Microsoft Outlook (1997, 2000, 2003, 2007, 2010). Winmail.dat contains all attachments and rich text message, and not all e-mail clients can recognize its format. Winmail Opener Pro is the solution. Winmail.dat Opener is the easiest, fastest, most reliable way for operations with them. It's completely frustration-free: just double-click the win mail.dat file and you're instantly presented with a list of its contents. Double-click the attached files to open them, or drag and drop them on the desktop. In most circumstances, you won't even need to leave your Mail program.