Email is an electirc version of mail. One email has the following structure which consists of two parts. The former is header, the latter is body. The separator between them is one null line (empty line). [Example] From: rudo@nuinui.net To: kenken@nuinui.net Subject: asobo. Hi, Kenken. I am Rudo. // rudo See RFC822 and RFC2822 for more details of definitions. Mailing list (ML) is forwarding mechanism of email. The program for it is called as ML driver. ML driver receives the email injected via MTA over the network, copy and redistributes it to members subscribed to the ML.