Truth be told, Spamcop disallows reports to be sent to email service providers (ESPs) if that email service provider doesn't require 100% confirmed opt-in of all clients. This effectively means no ESPs receive Spamcop reports, as just about any ESP is going to allow a client to upload a list. There's legitimate reasons for this; if people opted-in during purchase doing a commerce purchase on a different platform, or if a company switches ESPs, for example. They have a list already ready for use, the people on the list did truly sign up to receive email messages from that company, a confirmed opt-in (or double opt-in) confirmation isn't necessary.
Some people may disagree with my take on when COI/DOI is required. That's fine, but that's not the point.
The point is, Spamcop explains this policy poorly. Their system has historically provided a misleading error message to their users saying that any given ESP is "refusing" reports from Spamcop -- making it sound like Spamcop wants to send the report, but the ESP will not allow them to do so. That is simply not the case.
Spamcop has long had this policy, though it's not well documented. (And to be clear; I think it's a perfectly fine policy. It's not what I would do if it were up to me, but it's not up to me and reasonable people can and often do disagree. I just wish it was better documented.)
Here's the best source of proof for this policy I can find online. This 2011 Spamcop forum discussion thread starts with a post from Spamcop (Cisco) employee Kelly Molloy explaining that "we decline to send [Spamcop reports to various ESPs] because our policy is to only send reports to ESPs that send only confirmed opt-in (COI) email."
She adds, "There are basically only a few reasons we don't send reports:
- 1) We know the entity listwashes.
- 2) Reports are bouncing.
- 3) The responsible party told us they didn't want reports.
- 4) It's a non-COI ESP."
And now you know. I'm documenting this information here, purely as a public service, to make it easier for the next interested party to find.