My old ISP use to change my external IP address all the time and to keep my DNS name on track I wrote this script:

#!/usr/bin/python
import smtplib
import urllib2
import time
import sys

def send_email():
  try:
    server = smtplib.SMTP('smtp', 587)#smtp address and port number

    server.starttls()
    #Next, log in to the server
    server.login("smtp username", "password")#username and password for smtp

    #def emailSend(ipaddress):
    to_addr="your email address"
    subject="IPaddress is changed"
    message="this is from your webserver:" + html
    from_addr="you@gmail.com"

    header  = 'From: %s\n' % from_addr
    header += 'To: %s\n' % to_addr
    header += 'Subject: %s\n\n' % subject
    message = header + message

    #Send the mail
    #msg = "\nHello!" # The /n separates the message from the headers
    time.sleep(10)	
    print "wait few seconds..."
    server.sendmail(from_addr, to_addr, message)
    #server.sendmail(from_addr, to_addr, message)
    print "done."
    return True 
  except:  
    print "Unexpected error:", sys.exc_info()[0]
  return False

response = urllib2.urlopen('http://myip.dnsdynamic.org')
html = response.read()
print html

f = open("/root/myip.txt", "r");
sss = f.read()
print f.read()
if sss != html:
  print 'write'
  ff = open("/root/myip.txt", "w");
  ff.write(html)
  ff.close()
  if send_email() == False:
    send_email()
else:
  print 'all good'

f.close()

I hope it will be useful to some one else!

Enjoy.