Spellcheck is in hot waters right now since we're using GoogieSpell (Google's spell checker) which requires the data to be send over SSL to google for alaysis. While some may not find this a problem, there are those that would like to see a server-side solution like aSpell or pSpell surface. Spell check works, and works well, as long as you have SSL open in PHP for use. Otherwise you're out of luck until a server-side solution can be found.
The search, is it just the headers or is it the body of the email too?