Ubuntu 14.04
Usando uma conta de email google, usando googles apps com dominio proprio.
Instalar pacotes
$ apt-get install ssmtp mailutils
Editar arquivo de configuração
$ vim /etc/ssmtp/ssmtp.conf
# The person who gets all mail for userids < 1000
# Make this empty to disable rewriting.
root=destino@email.com
# The place where the mail goes. The actual machine name is required no
# MX records are consulted. Commonly mailhosts are named mail.domain.com
#mailhub=mail
# Where will the mail seem to come from?
rewriteDomain=futuria.com.br
# The full hostname
hostname=backup-server
# Are users allowed to set their own From: address?
# YES - Allow the user to specify their own From: address
# NO - Use the system generated From: address
FromLineOverride=YES
mailhub=smtp.googlemail.com:587
AuthUser=user@futuria.com.br
AuthPass=password
FromLineOverride=YES
UseTLS=YES
UseSTARTTLS=YES