Replying to or originating mail. You can use the reply command to set up a response to a message, sending it back to the person who it was from. Other escapes will set up subject fields, add and delete recipients to the message and allow you to escape to an editor to revise the message or to a shell to run some commands. Ending a mail processing session. Messages which have been examined go to your mbox file unless they have been deleted in which case they are discarded.
Unexamined messages go back to the post office.
Personal and systemwide distribution lists. The current list of such aliases can be displayed with the alias command in . In mail you send, personal aliases will be expanded in mail sent to others so that they will be able to reply to the recipients. System wide aliases are not ex- panded when the mail is sent, but any reply returned to the machine will have the system wide alias expanded as all mail goes through sendmail. Like print but also prints out ignored header fields.