you can use 'email' or 'emailx' command.
(1) $ vim /etc/mail.rc # or # vim /etc/nail.rc
set from = [email protected] #
set smtp = smtp.exmail.gmail.com #gmail's smtp server
set smtp-auth-user = [email protected] #sender's email address
set smtp-auth-password = xxxxxxx #get from gmail, not your email account passwd
set smtp-auth=login
(2) $ echo "Pls remember to remove unused ons topics!" | mail -s "waste topics" -a a.txt [email protected] #send to group user '[email protected]'