You can easily include all or part of previous messages, or the message you are responding to, including point by point responses to questions, etc. Difficult to completely erase and destroy. No unique signature. America On-line, CompuServe, or Microsoft Network, Prodigy, Genie, etc. Compuserve users replace the comma in their numerical ID with a period.
Most universities have searchable phonebooks which include email addresses.
This is complicated, and is much better done by manipulating the email on your UNIX machine using a PC email program such as Eudora or Pegasus. However, you can handle many email chores directly this way from your UNIX machine. Another problem is, that each keystroke is subject to delays due to high internet traffic while you're composing email, and you may be subject to high phone charges if you're direct dialing into your account from a distance. The Elm UNIX mail program is no longer being actively supported and its development has stagnated. I have no experience with it.