Do you mean how to send out a email to a distribution list without others on the list being able to see the people on the list, or do you mean how to send out a email so that no one knows it is you sending it?

If it is the first one, your email client should have that functionality built in.  Or if using something like Outlook or Thunderbird, just put everyone you send it to on the "bcc" send to line instead of the "to" or "cc" line. 

If it is the latter, it is called email spoofing and is illegal in many jurisdictions.  This is often used by spammers and scammers.

If you could provide a little more detail on what you want to do, and what email client you use perhaps we could help you a little more.  If it is about spoofing, I will not be interested in helping.

George