Configurar y enviar correos desde gmail por la terminar de Linux-Ubuntu

Paso 1:
sudo apt-get install postfix

Paso 2:
sudo nano /etc/postfix/main.cf

relayhost = [smtp.gmail.com]:587

# enable SASL authentication
smtp_sasl_auth_enable = yes
# disallow methods that allow anonymous authentication.
smtp_sasl_security_options = noanonymous
# where to find sasl_passwd
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
# Enable STARTTLS encryption
smtp_use_tls = yes
# where to find CA certificates
smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt

Paso 3:
sudo touch /etc/postfix/sasl_passwd
[smtp.gmail.com]:587 CorreoElectronico@gmail.com:MiContraseña

Paso 4:
sudo postmap /etc/postfix/sasl_passwd

Paso 5:
sudo postfix reload

Paso 6:
sudo apt-get install mailutils

Paso 7 Como enviar correos:
mail user@example.com
Cc:
Subject:

echo "El mensaje a enviar" | mail user@example.com
echo "El mensaje a enviar" | mail -s "Asunto" user@example.com
echo "El mensaje a enviar" | mail -a fichero.ext user@example.com