IP-based method

[phillipp]

Hey @korny

just an idea, because it might be easier to scale: we once had the idea to perform a lookup of the ip addreses of the MX records of the domains in the list and generate a list of the mailserver IPs.

Then the e-mail validation cloud check the MX record of the email domain against that list. It's much harder to get more IP addresses than domains, so that might be a more effective list to manage.

Just an idea, maybe you find it worth looking into.

Phillipp

[korny]

Great idea, but I'm not sure it actually works for the most problematic providers.

You can do the lookup in Ruby using resolv. But the latest example from 10minutemail.net (tipsb.com) resolves to four different IPs:

["li991-34.members.linode.com", 10], ["li1175-43.members.linode.com", 10], ["li984-13.members.linode.com", 10], ["li335-83.members.linode.com", 10]

which is not really helpful if these are throw-away instances.

Also, the blacklist check needs to be fast - a DNS lookup can take a while. If we could rely on some public blacklist service, and update the list behind the scenes every hour or so, that would be awesome...

[motionless]

I know this issue is old. My PR - https://github.com/phillipp/spam_email/pull/97 might address that issue in a different way but also looking up the MX record. I'd appreciate your feedback.