Add Emoticon at my Simplenews Newsletter's subject
If you're talking text-based emoticon (e.g. ":)", ":D") then the answer is yes. If you're talking Unicode emoji-character based emoticons (e.g. ) then the answer is maybe. While Drupal sends out UTF-8 encoded emails, support for display of the emoticons depends totally on recepient's email client so your results will vary.