code: def is_valid_email(email):
      
      import re
  
      qtext = '[^\\x0d\\x22\\x5c\\x80-\\xff]'
      dtext = '[^\\x0d\\x5b-\\x5d\\x80-\\xff]'
      atom = '[^\\x00-\\x20\\x22\\x28\\x29\\x2c\\x2e\\x3a-\\x3c\\x3e\\x40\\x5b-\\x5d\\x7f-\\xff]+'
      quoted_pair = '\\x5c[\\x00-\\x7f]'
      domain_literal = "\\x5b(?:%s|%s)*\\x5d" % (dtext, quoted_pair)
      quoted_string = "\\x22(?:%s|%s)*\\x22" % (qtext, quoted_pair)
      domain_ref = atom
      sub_domain = "(?:%s|%s)" % (domain_ref, domain_literal)
      word = "(?:%s|%s)" % (atom, quoted_string)
      domain = "%s(?:\\x2e%s)*" % (sub_domain, sub_domain)
      local_part = "%s(?:\\x2e%s)*" % (word, word)
      addr_spec = "%s\\x40%s" % (local_part, domain)
  
      email_address = re.compile('\A%s\Z' % addr_spec)
      if email_address.match(email):
          return True
      return False
docs: RFC822 Email Address Regex
      --------------------------
  
      Originally written by Cal Henderson
      c.f. http://iamcal.com/publish/articles/php/parsing_email/
  
      Translated to Python by Tim Fletcher, with changes suggested by Dan Kubb.
  
      Licensed under a Creative Commons Attribution-ShareAlike 2.5 License
      http://creativecommons.org/licenses/by-sa/2.5/