Improve out of date spam by verifying if the email address domain exists

[jelly]

Use python-email-validator to verify if a mx record exists for the email domain:

from email_validator import validate_email, caching_resolver
resolver = caching_resolver(timeout=10)
>>> valid = validate_email('ba@lmaoaooaa.com', dns_resolver=resolver)

• can we use memcached for caching mx records or do we not have to care as we have a local resolver.