A family of Microsoft word processing software products for creating web, email, and print documents.
As you have discovered, Word document format and html format are entirely different from one another. You will get a better idea of the issues involved if you use Word's web layout view.
I am not familiar with the vagaries of the Mac versions of Office, but Outlook html format has some peculiarities of its own to contend with. You might be better creating a web page and linking to it (given that some potential recipients will use plain text viewing).