If you're viewing this on www.spamresource.com, or if you click through to the site from your RSS reader, you'll now notice a "Co-reg Mail Received" section just to the right of the post on the site. This highlights IP addresses that have recently sent mail to the mailboxes that I use to track mail sent by "co-registration" or "lead generation" senders. Companies in this space often buy "feeds" or "feed paths" from other companies, and there is much data sharing back and forth. I just wanted to start tracking who's actively sending mail to my accounts, and this was a quick and easy way to do it. Keep an eye out as I update this section with more information over time. Might be neat to see how many emails this mailbox has received, how many times an IP address has been seen, etc.
I'm not alleging that this mail is spam, and most of the mail I see seems to comply with US federal law. That's not to say that senders in this space don't engage in practices that can cause significant deliverability issues. If you and a thousand other senders are all mailing to the same email lists, it seems as though a "tragedy of the commons" effect could apply, wherein ISPs find none of the senders to be sending desirable, wanted mail.
As always, your feedback is welcome.