Testing the deliverability of the actual email address? #165
Description
Currently, the deliverability check only verifies whether the MX DNS record resolves. However, many spam bots use email addresses from existing domains, either by using an orphaned address (which then usually is over quota) or just generating a random local part (which then is undeliverable).
What would you think about adding an optional validation step which builds a real connection to the MX host(s), sends the MAIL FROM and RCPT TO commands as if it was wanting to send an email, and then examines the replies from the SMTP server to see whether this specific email address would be accepted?
I'm currently using such an algorithm and it catches a lot of spam registrations. I want to switch to python-email-validator, so I would be willing to provide a patch if you would accept it. I have read about your high standards regarding test coverage and documentation, and I am 100% ready to (try to) fulfill that. But on the other hand, I see that such a feature would significantly extend the scope of the library, so I would understand if you said you don't want to open that can of worms.
FWIW, this is what I currently use.