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 ...

A file extension is a suffix that is added to the end of a file name after a dot. It is usually two to four letters long. File extensions help Windows and other operating systems to know the standard ...

The problem can occur when the Word file you are trying to open has a different file extension than the file you are attaching. It happens when you convert the file manually. There can be other ...