Awesome job!
One remark though:
That’s rare but, some SMTP define a catchall email address. Meaning all emails using this domain seems valid even if they are not.
I plan to set my email exactly like that. And then I will have emails like hackernews@mydomain.com or linkedin@mydomain.com etc. so I can keep track of which organization got my email from where.
Your package wants to deem such addresses invalid? I understand some spam orgs use techniques like these but many people use them with valid reasons.
