Shell Programming and Scripting

#!/bin/ksh
set -x
SUB="Test Email"
Mail_Body="This is for testing"
Send_Mail_HTML()
{
        (
         echo "FROM: abcd@test.com"
         echo "To: abcd@test.com"
         echo "Subject: $SUB"
         echo "MIME-Version: 1.0"
         echo "Content-Type: text/html"
         echo "Content-Disposition: inline"
         cat "$Mail_Body"
        ) | /usr/sbin/sendmail -t
}
##################Main Script Block############
Send_Mail_HTML

$ ksh test_mail.sh
+ SUB=Test Email
+ Mail_Body=This is for testing
+ Send_Mail_HTML
cat: cannot open This is for testing