SMTP

apt-get install msmtp-mta
apt-get install mailutils 
apt-get install msmtp ca-certificates

/etc/mstmprc

defaults
tls on
tls_starttls on
tls_trust_file /etc/ssl/certs/ca-certificates.crt

account default
host smtp.gmail.com
port 587
auth on
user myguiandroid@gmail.com
password xyz
from myguiandroid@gmail.com
logfile /var/log/msmtp.log

test

echo "Subject: test\nthis is the body" | msmtp --debug --from=default -t mymail@gmail.com

cron

04 19 * * * echo "Subject: backup\n"$(rsnapshot daily) | msmtp --from=default -t mymail@gmail.com