apt-get install postfix

# mail user1@gmail.com
subject: TEST <enter>
This is a test message <enter>
. <enter>

Another way to email

# METHOD1 - none interactive use of mail command (good for scripting) - includes subject line and body text. 2 lines of code and saves body of email to file.
echo "This is the body of the email" > body.txt
mail -s "Todays News" user1@gmail.com < body.txt

# METHOD2 - none interactive use of mail command (good for scripting) - includes subject line and body text. One line, body is not saved to file (saving disk space)
echo "This is the body of the email" | mail -s "Todays News" user1@gmail.com

cd ~

mkdir -p ipchange/logs

cd ipchange

# create the scripts that will run and email when ip changed
touch ipchange.sh
chmod +x ipchange.sh

# create the scripts that will email current wan ip (even when its not changed)
touch iplog.sh
chmod +x iplog.sh

vim ipchange.sh

#!/bin/bash
# What this script does: this one mails you the ip if it changes
# change above to !/bin/sh if you dont have /bin/bash and have sh instead

#################################
# **** set these variables **** #
#################################

# Which emails will receive the update/alert. Can have one or many. If many space delimited.
EMAIL_DEST="user1@email.com user2@email.com 5551234321@tmomail.net"

# SUBJECT_COMMENT can be set to empty or to any text, it will appear in the subject line so its nice to put the hostname, or perhaps some keyword/phrase that will let you know what server the email came from
# Pick any of these SUBJECT_COMMENTs or create your own. Or leave the current one which is an empty SUBJECT_COMMENT
SUBJECT_COMMENT=""
### SUBJECT_COMMENT="My Awesome Server"
### SUBJECT_COMMENT="`hostname` - My Awesome Server"

# OLD_IP_FILE pick a file which will store the IP in a safe place. Dont put this in /tmp as that location is cleared upon reboot. It best to keep this in /root, /etc, or /var/log (permanent storage)
OLD_IP_FILE="/var/log/old_ip.txt"

#######################
# **** main code **** #
#######################

# get current ip
IP=`curl icanhazip.com 2> /dev/null`
# get last ip that we saved on the last run of this (see very bottom of script)
OLD_IP=`cat "${OLD_IP_FILE}"`

# check if old ip and new ip are the same. if they are the same dont do anything. if they arent email every email in email_dest
if [ "${IP}" = "${OLD_IP}" ]; then
    MESSAGE="[`date`] ipchange script - IP is the same: ${IP} so not emailing"
    echo "${MESSAGE}"
    logger "${MESSAGE}"
else
    # ANOTHER WAY TO EMAIL: (echo "From: home@homesystem.com"; echo "To: myemail@domain.com"; echo "Subject: IP Address Update"; echo; echo "Computer's IP Changed. The new IP is:"; cat index.html) | sendmail -f home@homesystem.com myemail@domain.com
    MESSAGE="[`date`] ipchange script - The new IP is: ${IP}"
    echo "${MESSAGE}"
    logger "${MESSAGE}"
    for CURRENT_EMAIL in ${EMAIL_DEST}; do
       echo "Emailing ${CURRENT_EMAIL}";
       echo "${MESSAGE}" | mail -s "IP CHANGED: ${SUBJECT_COMMENT}" "${CURRENT_EMAIL}";
    done
fi
# save current ip as the old ip, as the next time this runs it will be the old ip
echo "${IP}" > "${OLD_IP_FILE}"

vim iplog.sh

#!/bin/bash
# This script will get your WAN / Public IP and email it to you (as definited in EMAIL_DEST)
# change above to !/bin/sh if you dont have !/bin/bash
# change the EMAIL_DEST and FOLDER variables to meet your needs
# this script should be run by the root user
# Set EMAIL_DEST to any email which should receive the alert. any number of emails that will get the alert (space character seperator/delimiter). If you just want one email, then only put one there, like this EMAIL_DEST="one@email.com"
EMAIL_DEST="user1@email.com user2@email.com 8015551234@tmomail.net" 
# The folder /root/ipchange should exist (but if it doesnt it will get created). Copys of the body which is sent will go there
FOLDER=/root/ipchange
# SUBJECT_COMMENT can be set to empty or to any text, it will appear in the subject line so its nice to put the hostname, or perhaps some keyword/phrase that will let you know what server the email came from
# Pick any of these SUBJECT_COMMENTs or create your own. Or leave the current one which is an empty SUBJECT_COMMENT
SUBJECT_COMMENT=""
### SUBJECT_COMMENT="My Awesome Server"
### SUBJECT_COMMENT="`hostname` - My Awesome Server"
# get the WAN IP and save to the variable IP
IP=`curl icanhazip.com 2> /dev/null`
# The FILE variable will be the filename of the file which will hold the body of the email
FILE="`date +D%D-T%T | tr / - | tr : -`"
mkdir -p ${FOLDER}/logs 2> /dev/null
# EMAIL_BODY is the full filename (with the path). The file refered by EMAIL_BODY contains the body text of the email which will be sent to each of the EMAIL_DESTINATIONS
EMAIL_BODY=${FOLDER}/logs/${FILE}
echo "Saving copy of email body to: ${EMAIL_BODY}"
echo ${FILE} ": THE IP IS:" ${IP} | tee ${EMAIL_BODY}
# send the same email to each of the emails listed in EMAIL_DEST
# EMAIL_DEST needs to have either 1 email, or more than one (as long as they are space delimited)
for CURRENT_EMAIL in ${EMAIL_DEST}; do
echo "Emailing ${CURRENT_EMAIL}";
mail -s "IP LOG: ${SUBJECT_COMMENT} ${FILE}" "${CURRENT_EMAIL}" < ${EMAIL_BODY};
done

crontab -e

# this logs the ip and emails it (twice a day)
# the @midnight is a shortcut for midnight, so that the iplog sends you your IP at midnight of every day
# the 0 12,18 * * * sends updates at noon and 6pm

@midnight /root/ipchange/iplog.sh
0 12,18 * * * /root/ipchange/iplog.sh
 
# this looks for email changes every 5 minutes
# If it were all start * * * * * it would check every minute but */5 makes it skip 5 minutes
 
*/5 * * * * /root/ipchange/ipchange.sh

# /etc/init.d/cron reload