We get it, using Word or Publisher and then saving as HTML is a very easy way to create message content. However, what you see in one program will change how your email is ultimately received.
Typically, it is not recommended that you copy formatted text from another platform into an email message because other platforms introduce inline styles and other things that may not be compatible with email messages. This unseen formatting can also negatively impact your deliverability.
If you must copy from Word or an external source, paste in your content using the Paste from Word tool.
This will strip out most of the extraneous code -- but even this tool is not impervious. Even with the Paste from Word tool, there are still some issues that you can run into, like invisible characters and hidden HTML elements that aren't visible until the message lands in your inbox or Deliverability Testing.