why are my attachments converting from word to rtf

Recently, for some unknown reason all of my attachments are converting from a word file to an rtf.  I have not had this problem before and cannot figure it out.  My documents are done in word and saved as a word file.  Then when I attach a document to an email it shows as an rtf file. Did I do something to change the default attachment? And if so, how do I change it ?  It is important to note that this if for my Hotmail account, which is now an outlook.com account.  I have found information on the website but found that it applied to the Microsoft office email and not Hotmail.