django email forms field.

emailfields.py

# coding: utf-8

import re

from django.forms.fields import CharField
from django.forms.widgets import EmailInput
from django.utils.deconstruct import deconstructible


class EmailValidator(object):
  
  message = _('Enter a valid email address.')
  code = 'invalid'

  user_part_regex = re.compile(r"^(?:(?:(?:(?:[a-zA-Z0-9_!#\$\%&'*+/=?\^`{}~|\-]+)(?:\.(?:[a-zA-Z0-9_!#\$\%&'*+/=?\^`{}~|\-]+))*)$"
                               r'|(?:"(?:\\[^\r\n]|[^\\"])*")))$',
                               re.IGNORECASE)
  domain_part_regex = re.compile(r"(?:(?:(?:(?:[a-zA-Z0-9_!#\$\%&'*+/=?\^`{}~|\-]+)(?:\.(?:[a-zA-Z0-9_!#\$\%&'*+/=?\^`{}~|\-]+))*)|(?:\[(?:\\[\x01-\x09\x0B-\x0c\x0e-\x7f]|[\x21-\x5a\x5e-\x7e])*\])))$",
                                 re.IGNORECASE)

  def __init__(self, message=None, code=None):
      if message is not None:
          self.message = message
      if code is not None:
          self.code = code

  def __call__(self, value):
      value = force_text(value)

      if not value or '@' not in value:
          raise ValidationError(self.message, code=self.code)

      user_part, domain_part = value.rsplit('@', 1)

      if not self.user_regex.match(user_part):
          raise ValidationError(self.message, code=self.code)

      if not self.domain_part_regex.match(domain_part):
          raise ValidationError(self.message, code=self.code)

    def __eq__(self, other):
        return (
            isinstance(other, EmailValidator) and
            (self.message == other.message) and
            (self.code == other.code)
        )


@deconstructible
class EmailField(CharField):
    widget = EmailInput
    default_validators = [EmailValidator()]

    def clean(self, value):
        value = self.to_python(value).strip()
        value = super(EmailField, self).clean(value)

        user_part, domain_part = value.rsplit('@', 1)

        return '{}@{}'.format(user_part, domain_part.lower())