We get it, using Word or Publisher and then saving as HTML is a very easy way to create message content, however, what you may see in one program will change how your email is ultimately received. Typically, it is not recommended that you copy formatted text over to an email message from another platform. Because these other platforms introduce inline styles and other special characters which may not be compatible with Email messages, what’s worse this formatting can also negatively impact your deliverability. If you must copy from Word or from an external source, paste in your content using the Paste from Word tool.
This will strip out most of the extraneous lines of 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, or even “hidden” HTML elements that wouldn’t be visible to you until the message lands in your inbox or Deliverability Testing.