How to send an email via router

In this page I describe how to send an email through a router (Asus RT-AC56U) - we use an Entware installation, so please refer to this page on how to install Entware on a router.
To send an email, we use a command line utility called "msmtp", compatible with most used command line utility "sendmail" (not included in Entware packages).
To install package "msmtp" we use the command line "opkg install msmtp".
After installing this package, we must setup the configuration file "/opt/etc/msmtprc". This file include all data regarding the SMTP server, these data must be provided by the email provider.
For more information about configuration file, please refer to MSMTP website.
This is a simple configuration file, we use Microsoft's Live SMTP server :

cat /opt/etc/msmtprc

account default
domain local
host smtp.live.com
port 25
protocol smtp
from [myemail]@hotmail.com
auth on
user [myemail]@hotmail.com
password [mypassword]
tls on
tls_starttls on
tls_certcheck off
syslog LOG_MAIL

Then we can use a script to send an email. This is a simple script used to send an email through "msmtp" command line utility - please remember that "from" email address of the script must be the same of the "from" email address of the configuration file:

#!/bin/sh

msmtp -v -t << EOF
From: [myemail]@hotmail.com
Subject: Router - sample email test
To: to_address@domain.xxx

This is a testing email sent by router through Entware.

EOF

exit 0