I have a few older Word documents with the following toolbar showing. If I save them in Office 2016 the toolbar is hidden and I do not know how to restore it. Since I did not create the original documents I am not sure what version (probably 2010) and what options were used to create this.
There are no Toolbars in Word 2016 and there hasn't been Word 2003.
To add the ability to Send Emails from Word 2016 you can add the Send function to your QAT (Quick Action Toolbar), see image below, or add it to either an existing or custom tab on Word's ribbon. Also look at the other "Send ..." email functions that are available in the All Commands category of QAT or Ribbon Customization.