Shell Programming and Scripting

export MAILTO=abc@xyz.com
        export CONTENT="/home/abc/list.html"
        (
        echo "Subject: $SUBJECT"
        echo "MIME-Version: 1.0"
        echo "Content-Type: text/html"
        echo "To: abc@xyz.com"
        #echo "Content-Disposition: inline"
        cat $CONTENT
        ) |  /usr/sbin/sendmail -t -i $MAILTO

The below code is perfectly working for sending the attachment alone:
( echo "to: abc@xyz.com"
  echo "from: abc@xyz.com" 
  echo "subject: sending file"
  echo "mime-version: 1.0"
  echo "content-type: multipart/related; boundary=xxxRANDOMSTRINGxxx"
  echo
  echo "--xxxRANDOMSTRINGxxx"
  echo "content-type: text/plain"
  echo
  echo "Attached is the audit info"
  echo
  echo "--xxxRANDOMSTRINGxxx"
  echo "content-type: text/html; name=newlist.txt"
  echo "content-transfer-encoding: base64"
  openssl base64 < /home/abc/list.csv ) | /usr/sbin/sendmail -t -i $MAILTO

( echo "to: abc@xyz.com"
echo "from: abc@xyz.com"
echo "subject: sending file"
echo "mime-version: 1.0"
echo "content-type: multipart/related; boundary=xxxRANDOMSTRINGxxx"
echo
echo "--xxxRANDOMSTRINGxxx"
echo "content-type: text/html"
echo
cat $CONTENT
echo "--xxxRANDOMSTRINGxxx"
echo "content-type: text/html; name=newlist.txt"
echo "content-transfer-encoding: base64"
openssl base64 < /home/abc/list.csv ) | /usr/sbin/sendmail -t -i $MAILTO

to="abc@xyz.com"
from="testing@xyz.com"
boundary=$(uuidgen -t)
content="/home/abc/list.html"
now=$(date +"%a, %d %b %Y %T %z")

sendmail -t <<EOF!
From: ${from}
To: ${to}
Date: ${now}
Subject: Sending file
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="${boundary}"

--${boundary}
Content-type: text/html; charset=utf-8
Content-Disposition: inline

$(cat $content)
--${boundary}
content-type: text/html
content-transfer-encoding: base64
content-disposition: attachment; filename="newlist.txt"

$(openssl base64 < /home/abc/list.csv)
--${boundary}--
EOF!