No idea but not sure the spam filters will like them ( no heart ) anyway ?
cpmcomputers
If you must try this
If you have Windows, simply press the Windows key + R and when the Run box appears, type in charmap and hit enter. It will bring up a chart of various symbols you can copy and paste.
If you're using a windows based OS you can press the ALT key in conjunction with the number 3 on your number pad. The result will be ¿...a heart. You can likewise use Shift + , (comma) to make a bracket < and follow it with the number 3... <3.
EDIT: This forum doesn't support the alt code library, however Yahoo, Gmail, etc, do.
In spite of all your efforts; in the end user settings are the final determiner of what displays. When I get an email with crap in the subject line it gets deleted without opening even if my spam filtering did not kill it.
All you will do is reduce the number of people who actually open the email.