How can you check if an IP is good or spammy? It would be nice to get an elastic IP in the cloud, test it for spamminess, and give back the bad ones. Catch and release fishing for IPs.
https://senderscore.org/ per https://news.ycombinator.com/item?id=9156312
http://whatismyipaddress.com/blacklist-check per https://news.ycombinator.com/item?id=11329371
http://multirbl.valli.org/ per https://news.ycombinator.com/item?id=11330382
This is because the big consumer mailbox providers often don't rely on public datasources for assessing reputation, and because reputation is tracked at the domain level, in addition to - or sometimes instead of - the IP level. For example, there have been some indications from Gmail that they no longer use IP reputation at all, starting a year or two ago.
And re: blacklists: +1 to Spamhaus, but in practice it's one of very few blacklists that have meaningful impact to net delivery.
I can believe it. I posted already about my experience with the free tier of Mailgun's service. I went through all their instructions about setting up the service and verifying my domain etc. but still had a lot of email rejected, especially by yahoo.com but also hotmail.com due to poor reputation IPs
Gmail.com typically delivered everything.
(I do not have anything to do with the product or team behind it)
(I am likewise unaffiliated.)
In years past, many RBLs would categorize IP Addresses by type. e.g. dynamic IPs assigned to DSL/Cable subscribers. This would enable a receving SMTP server to check if the email came from an ISP subscriber, rather than an email server. If so, it was usually a good guage that the email was "spammy", because it was sent by a subscriber's infected computer.
In this sense, it was (and may still be) possible to simply block, or at least score differently, email from any/all AWS Elasic IPs.
Neither, though, helps with checking if one of the big providers, like Google, would not like your IP. For those, you have to send an email and watch/parse the SMTP error responses.