Subtextual – eMail Communications Tool
http://www.subtextual.com/

Subtextual is a plugin for Microsoft Outlook designed to empower email users by allowing you to add additional information to selected individuals of an email. Avoid costly miscommunication errors by saying exactly what you mean to the right person, whether they are in the To, Cc or Bcc field. This has been added to the tools section of Research Resources Subject Tracer™ Information Blog.