If you are talking about the @wordpress-outsourcing[.]com spam, it's a Google Group they add everyone to then post in the group. I don't think that requires verification. I've had to dig into the email headers to find the original list unsubscribe and post to it manually. I've also just block any email with that domain name from our support tool.
_______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop