msmtp

install

# apt install msmtp msmtp-mta

Config

# cat << EOF > /etc/msmtprc

defaults
auth           on
tls            on
tls_starttls   on
tls_trust_file /etc/ssl/certs/ca-certificates.crt
logfile        /var/log/msmtp

account        gmail
auth           plain
host           smtp.gmail.com
port           587
from           sender@gmail.com
user           sender@gmail.com
password       XXXXXXXXXXXXXXXXXXXXXXXX

account default : gmail
EOF
# chown root:msmtp /etc/msmtprc
# chmod 640 /etc/msmtprc

Test

$ echo "sample message" | mail -s "subject" email@address