Python alternative to getadsmtp.pl; Runs faster and performs the same AD query for valid SMTP recipients. Credits noted in the comments.

getadsmtp.py

#!/usr/bin/env python

#Credits: Marc Smith, http://marcitland.blogspot.com/2011/02/python-active-directory-linux.html
#	  DarkPixel, https://github.com/darkpixel/scripts/blob/master/getadsmtp.py
#	  JR, http://liveaverage.com

import sys, ldap, argparse
import ldap.modlist as modlist
from ldap.controls import SimplePagedResultsControl

parser = argparse.ArgumentParser(formatter_class=argparse.ArgumentDefaultsHelpFormatter, description="Retrieve e-mail addresses from an LDAP server in postfix format")
parser.add_argument('-c', '--connect', required=True, action='store', help='The host to connect to (AD/Exchange Server)')
parser.add_argument('-r', '--port', action='store', help='Port to use for connecting, defaults to 636')
parser.add_argument('-u', '--user', action='store', required=True, help='Username to use (either cn=blah,dc=cust,dc=local or [email protected] format)')
parser.add_argument('-p', '--password', action='store', required=True, help='Password')
parser.add_argument('-o', '--ou', action='store', required=True, help='Org Unit (Base DN) to export from')
arg = parser.parse_args()

LDAP_SERVER = 'ldaps://%s:%s' %(arg.connect, arg.port or '3269')
BIND_DN = arg.user
BIND_PASS = arg.password
USER_FILTER = "(& (mailnickname=*) (| (objectClass=publicFolder)(&(objectCategory=person)(objectClass=user)(!(homeMDB=*))(!(msExchHomeServerName=*)))(&(objectCategory=person)(objectClass=user)(|(homeMDB=*)(msExchHomeServerName=*)))(objectCategory=person)(objectCategory=group)(objectClass=msExchDynamicDistributionList) ) (!(objectClass=contact)) )"
USER_BASE = arg.ou
PAGE_SIZE = 500

# LDAP connection
try:
  ldap.set_option(ldap.OPT_X_TLS_REQUIRE_CERT, ldap.OPT_X_TLS_NEVER)
  ldap_connection = ldap.initialize(LDAP_SERVER)
  ldap_connection.set_option(ldap.OPT_REFERRALS, 0)
  ldap_connection.set_option(ldap.OPT_PROTOCOL_VERSION, 3)
  ldap_connection.set_option(ldap.OPT_X_TLS,ldap.OPT_X_TLS_DEMAND)
  ldap_connection.set_option( ldap.OPT_X_TLS_DEMAND, True )
  ldap_connection.set_option( ldap.OPT_DEBUG_LEVEL, 255 )
  ldap_connection.simple_bind_s(BIND_DN, BIND_PASS)
except ldap.LDAPError, e:
  sys.stderr.write('Error connecting to LDAP server: ' + str(e) + '\n')
  sys.exit(1)

# Lookup usernames from LDAP via paged search
paged_results_control = SimplePagedResultsControl(
  ldap.LDAP_CONTROL_PAGE_OID, True, (PAGE_SIZE, ''))
accounts = []
pages = 0
while True:
  serverctrls = [paged_results_control]
  try:
      msgid = ldap_connection.search_ext(USER_BASE,
                                         ldap.SCOPE_SUBTREE,
                                         USER_FILTER,
                                         attrlist=['proxyAddresses'],
                                         serverctrls=serverctrls)
  except ldap.LDAPError, e:
      sys.stderr.write('Error performing user paged search: ' +
                       str(e) + '\n')
      sys.exit(1)
  try:
      unused_code, results, unused_msgid, serverctrls = \
                 ldap_connection.result3(msgid)
  except ldap.LDAPError, e:
      sys.stderr.write('Error getting user paged search results: ' +
                       str(e) + '\n')
      sys.exit(1)
  for result in results:
      pages += 1
      accounts.append(result)
  cookie = None
  for serverctrl in serverctrls:
      if serverctrl.controlType == ldap.LDAP_CONTROL_PAGE_OID:
          unused_est, cookie = serverctrl.controlValue
          if cookie:
              paged_results_control.controlValue = (PAGE_SIZE, cookie)
          break
  if not cookie:
      break

# LDAP unbind
ldap_connection.unbind_s()

#Address Counter:
ac = 0

for entry in accounts:
  #DEBUG: Convert entry to string and print:
  #print "%s" % str(entry)
  if hasattr(entry[1], 'has_key') and entry[1].has_key('proxyAddresses'):
      addresses = entry[1]['proxyAddresses']
      for addr in addresses:
          if 'smtp:' in addr.lower():
	      ac += 1
	      print "%s OK" % (addr.lower().split('smtp:')[1]) 
	      #DEBUG: Convert addr to string and print:
	      #print "%s" % str(addr)
print "# %d results" % len(accounts)
#print "%d proxyAddresses" % ac

Revised the original script's LDAP filter to include Public Folders when scraping Exchange for valid proxyAddresses. I found out the hard way it wasn't adding PFs with associated mail addresses.