Alain Kelder is a Giant Dork

SMTP test message via shell script using netcat instead of telnet

I've always used telnet for SMTP testing. Finally, got sick of copy/pasting and decided to write a quick script. But scripting telnet is a pain. Netcat to the rescue!

Call the script with the following arguments:

$ ./smtp.netcat.test mx.example.com 25 from@example.com to@example.com

And here's the script:

#!/bin/bash
# script to send test mail with netcat. 
# expects the following arguments:
# 1. recepient mail server
# 2. port (typically 25 or 465)
# 3. mail from (e.g. from@example.com)
# 4. mail to (e.g. to@example.com)

# for mail_input function
from=$3
to=$4

# error handling
function err_exit { echo -e 1>&2; exit 1; }

# check if proper arguments are supplied
if [ $# -ne 4 ]; then
  echo -e "\n Usage error!"
  echo " This script requires four arguments:"
  echo " 1. recepient mail server"
  echo " 2. port (typically 25 or 465)"
  echo " 3. mail from (e.g. from@example.com)"
  echo " 4. mail to (e.g. to@example.com)"
  exit 1
fi

# create message
function mail_input { 
  echo "ehlo $(hostname -f)"
  echo "MAIL FROM: <$from>"
  echo "RCPT TO: <$to>"
  echo "DATA"
  echo "From: <$from>"
  echo "To: <$to>"
  echo "Subject: Testing one two three"
  echo "This is only a test. Please do not panic. If this works, then all is well, else all is not well."
  echo "In closing, Lorem ipsum dolor sit amet, consectetur adipiscing elit."
  echo "."
  echo "quit"
}

# test
#mail_input

# send
mail_input | nc $1 $2 || err_exit