Command-line utility to reliably verify an e-mail address. (Python)

email-verify

#!/usr/bin/python
"""
Description:
	Command-line tool to validate an email address.
	After verifying e-mail address by pattern matching, checks the validity with the SMTP server.

Usage:
	./email-verify somebody@example.com

# (c) 2013 Manu Manjunath
# Extended from (c) 2012 Syrus Akbary <me@syrusakbary.com>
# Extended from (c) 2011 Noel Bush <noel@aitools.org>
# This code is made available to you under the GNU LGPL v3.
"""

import sys, re

host_check = True
smtp_check = True
try:
	import DNS, socket
except:
	host_check = False
try:
	import smtplib
except:
	smtp_check = False

WSP = r'[ \t]'	# see 2.2.2. Structured Header Field Bodies
CRLF = r'(?:\r\n)' # see 2.2.3. Long Header Fields
NO_WS_CTL = r'\x01-\x08\x0b\x0c\x0f-\x1f\x7f' # see 3.2.1. Primitive Tokens
QUOTED_PAIR = r'(?:\\.)' # see 3.2.2. Quoted characters
FWS = r'(?:(?:' + WSP + r'*' + CRLF + r')?' + WSP + r'+)'	# see 3.2.3. Folding white space and comments
CTEXT = r'[' + NO_WS_CTL + r'\x21-\x27\x2a-\x5b\x5d-\x7e]' # see 3.2.3
CCONTENT = r'(?:' + CTEXT + r'|' + QUOTED_PAIR + r')' # see 3.2.3 (NB: The RFC includes COMMENT here as well, but that would be circular.)
COMMENT = r'\((?:' + FWS + r'?' + CCONTENT + r')*' + FWS + r'?\)' # see 3.2.3
CFWS = r'(?:' + FWS + r'?' + COMMENT + ')*(?:' + FWS + '?' + COMMENT + '|' + FWS + ')' # see 3.2.3
ATEXT = r'[\w!#$%&\'\*\+\-/=\?\^`\{\|\}~]' # see 3.2.4. Atom
ATOM = CFWS + r'?' + ATEXT + r'+' + CFWS + r'?' # see 3.2.4
DOT_ATOM_TEXT = ATEXT + r'+(?:\.' + ATEXT + r'+)*'	# see 3.2.4
DOT_ATOM = CFWS + r'?' + DOT_ATOM_TEXT + CFWS + r'?' # see 3.2.4
QTEXT = r'[' + NO_WS_CTL + r'\x21\x23-\x5b\x5d-\x7e]' # see 3.2.5. Quoted strings
QCONTENT = r'(?:' + QTEXT + r'|' + QUOTED_PAIR + r')' # see 3.2.5
QUOTED_STRING = CFWS + r'?' + r'"(?:' + FWS + r'?' + QCONTENT + r')*' + FWS + r'?' + r'"' + CFWS + r'?'
LOCAL_PART = r'(?:' + DOT_ATOM + r'|' + QUOTED_STRING + r')' # see 3.4.1. Addr-spec specification
DTEXT = r'[' + NO_WS_CTL + r'\x21-\x5a\x5e-\x7e]' # see 3.4.1
DCONTENT = r'(?:' + DTEXT + r'|' + QUOTED_PAIR + r')' # see 3.4.1
DOMAIN_LITERAL = CFWS + r'?' + r'\[' + r'(?:' + FWS + r'?' + DCONTENT + r')*' + FWS + r'?\]' + CFWS + r'?' # see 3.4.1
DOMAIN = r'(?:' + DOT_ATOM + r'|' + DOMAIN_LITERAL + r')' # see 3.4.1
ADDR_SPEC = LOCAL_PART + r'@' + DOMAIN # see 3.4.1

# A valid address will match exactly the 3.4.1 addr-spec.
VALID_ADDRESS_REGEXP = '^' + ADDR_SPEC + '$'

if __name__ == '__main__':
	if len(sys.argv)!=2:
		print "Pass e-mail ID as param to this script"
		quit()
	email = sys.argv[1]
	try:
		print "Checking pattern...",
		assert re.match(VALID_ADDRESS_REGEXP, email) is not None
		print "[VALID]"		
		hostname = email[email.find('@')+1:]	
		if host_check:
			try:
				print "Verifying host...",
				sys.stdout.flush()
				result = socket.getaddrinfo(hostname, None)
				print "[VALID]"
				print "Checking if '%s' can receive e-mail..." % hostname,
				sys.stdout.flush()
				DNS.DiscoverNameServers()
				mx_hosts = DNS.mxlookup(hostname)
				if smtp_check:
					if len(mx_hosts) > 0:
						print "[Yes]"
						print "Verifying email...",
						sys.stdout.flush()
						isValid = True
						verificationRejected = False
						connectionError = False
						for mx in mx_hosts:
							try:
								smtp = smtplib.SMTP()
								smtp.connect(mx[1])
								status, _ = smtp.helo()
								if status != 250:
									continue
								smtp.mail('emailchecker@emailchecker.com')
								status, _ = smtp.rcpt(email)
								if status == 250:
									print "[VALID, says %s]" % (mx[1])
								else:
									print "[INVALID, says %s]" % (mx[1])
								sys.stdout.flush()	
								break
							except smtplib.SMTPServerDisconnected: #Server not permits verify user
								verificationRejected=True
								continue
							except smtplib.SMTPConnectError:
								connectionError=True
								continue
						if connectionError:
							print "Connection error. You may want to retry."
						elif verificationRejected:
							print "Server(s) refused to validate e-mail."
					else:
						print "[NOT FOUND]\n(Domain '%s' doesn't have any registered MX records)" % hostname
				else:
					print "Warning: Skipped e-mail verification for %s" % email
			except socket.gaierror:
				print "Invalid hostname '%s'" % hostname
			except DNS.ServerError:
				print "Host %s could not be reached/connected to" % hostname
			except DNS.Base.TimeoutError:
				print "Host %s did not respond within time" % hostname
		else:
			print "Warning: Skipped checking validity of domain '%s'\nInstall Python packages 'DNS' (http://sourceforge.net/projects/pydns/) and 'socket' for detailed verification" % hostname
	except AssertionError: 
		print "Error: '%s' doesn't match a valid e-mail pattern" % email