If you've ever received a forward from an Outlook user in Mail.app containing an attached winmail.dat file, you probably scratched your head wondering why this strange file ended up in your inbox and ...

Letter Opener converts winmail.dat attachments on the fly, so you can actually see and use the attachments the sender intended you to have. [Editor’s note: The following review is part of Macworld’s ...

Many times when receiving mail attachments with the new Exchange-enabled Microsoft Entourage v.X from Windows users, you will get a winmail.dat file that is inaccessible under Mac OS X. Alan Sill ...

There are loads of file types swimming around our computers at any given time — most of which exist to supplement the programs we use or play (or allow them to function in the first place). The most ...

We keep getting e-mail attachments in winmail.dat files and can’t open them. What’s going on? Is there a utility that can extract the attachments from these? When Outlook or Outlook Express users send ...

If you're one of the people who own a stylus or touchscreen-capable Windows PC, then there's a high chance there's a file on your computer that has slowly collected sensitive data for the past months ...

We’ve all seen mysterious .dat file attachments in our inboxes from time to time. In most cases the .dat attachment originates in Microsoft Outlook, which produces outgoing messages using a slightly ...

However, things changed with Windows 11/10/8. In Windows 11/10/8, Index.dat files are not used by Internet Explorer 10. The indexing functions are being implemented within a Microsoft database system.

.dat can mean many things. data of any type quite often ends up with these extensions. How about using the app that created them? You can also try viewing them in notepad.