Can you please be more specific? How was the HTML file created? Are you using the HTML for the body of your e-mail task within the Automation script?
Only thing I can think of is that TDP can control the encoding of files, and this control is either at the Editor (Editor->Character Encoding from the pull-down menu) or via the options, as in the screen snap below. Maybe playing with the encoding may help?
Just curious, have you opened a Support ticket to see if Support can identify the issue?
