etes · March 18, 2020 12:44 · Jan 16, 2009 · Jan 16, 2009 · Jan 16, 2009
diff --git a/smtpcheck.py b/smtpcheck.py
@@ -16,6 +16,8 @@
   from you. It does not in any way, shape or form conform to standard confirmed
   opt-in practices. Anyone who uses this technique and then begins sending
   email without going through a confirmation loop is a spammer.
+
+  - Zach White
 """
 usage = 'usage: %prog [options] email1 [email2 [...]]'
 import logging

diff --git a/smtpcheck.py b/smtpcheck.py
@@ -1,6 +1,22 @@
 #!/usr/bin/env python
-# Check that a particular email address exists.
-# Adam Blinkinsop <[email protected]>
+"""
+Check that a particular email address exists.
+Adam Blinkinsop <[email protected]>
+
+WARNING:
+  Checking email addresses in this way is not recommended, and will lead to
+  your site being listed in RBLs as a source of abusive traffic. Mail server
+  admins do like it when they get connections that don't result in email being
+  sent, because spammers often use this technique to verify email addresses.
+  (Incidentally, a lot of sites will accept bad addresses and only reject after
+  the DATA portion of the SMTP transactions, for this very reason.)
+
+  Additionally, the check is not good in most situations because it doesn't do
+  any verification that the owner of the email address wants to receive email
+  from you. It does not in any way, shape or form conform to standard confirmed
+  opt-in practices. Anyone who uses this technique and then begins sending
+  email without going through a confirmation loop is a spammer.
+"""
 usage = 'usage: %prog [options] email1 [email2 [...]]'
 import logging
 import os

diff --git a/smtpcheck.py b/smtpcheck.py
@@ -0,0 +1,71 @@
+#!/usr/bin/env python
+# Check that a particular email address exists.
+# Adam Blinkinsop <[email protected]>
+usage = 'usage: %prog [options] email1 [email2 [...]]'
+import logging
+import os
+import re
+import smtplib
+
+# Match the mail exchanger line in nslookup output.
+MX = re.compile(r'^.*\s+mail exchanger = (?P<priority>\d+) (?P<host>\S+)\s*$')
+
+def verify(addr, local_addr='[email protected]'):
+  """Verify the existance of a single email address."""
+  logging.debug('Verifying existance of %r', addr)
+  # Find mail exchanger of this address.
+  host = addr.rsplit('@', 2)[1]
+  p = os.popen('nslookup -q=mx %s' % host, 'r')
+  mxes = list()
+  for line in p:
+    m = MX.match(line)
+    if m is not None:
+      mxes.append(m.group('host'))
+  logging.debug('Found %d mail exchangers for %s.', len(mxes), host)
+  if len(mxes) == 0:
+    return False
+  else:
+    host = mxes[0]
+
+  # Connect to the mail server and check.
+  logging.debug('Checking address with %s.', host)
+  server = smtplib.SMTP(host)
+  server.ehlo_or_helo_if_needed()
+  code, response = server.docmd('mail from:', '[email protected]')
+  logging.debug('MAIL FROM command returned %d: %r', code, response)
+  code, response = server.docmd('rcpt to:', addr)
+  logging.debug('RCPT TO command returned %d: %r', code, response)
+  server.quit()
+  return (code // 100 == 2)
+
+def main(*args, **opts):
+  """Handle execution from the command line."""
+  for addr in args:
+    if verify(addr, local_addr=opts['local_addr']):
+      print '%r exists.' % addr
+    else:
+      print '%s DOES NOT exist.' % addr
+
+def flags():
+  """Parse options from the command line."""
+  from optparse import OptionParser
+  parser = OptionParser(usage=usage)
+  parser.add_option('-f', '--from',
+      dest='local_addr', default='[email protected]',
+      help='email address to appear to be from')
+  parser.add_option('-d', '--debug',
+      action='store_const', const=logging.DEBUG, dest='log_level',
+      help='log everything')
+  parser.add_option('-v', '--verbose',
+      action='store_const', const=logging.INFO, dest='log_level',
+      help='log everything but debugging messages')
+  parser.add_option('-q', '--quiet',
+      action='store_const', const=logging.ERROR, dest='log_level',
+      help='only log errors')
+  opts, args = parser.parse_args()
+  logging.basicConfig(level=opts.log_level)
+  return opts, args
+
+if __name__ == '__main__':
+  opts, args = flags()
+  main(*args, **opts.__dict__)