A file extension, or file name extension, is the letters immediately shown after the last period in a file name. For example, the file extension.txt has an extension of .txt. This extension allows the ...

Q. I sometimes receive e-mail messages with a “winmail.dat” file attached that I cannot open. Why does this happen, and what can I do to fix it? A. The winmail.dat file usually appears because various ...

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 ...