The only way you'd get am accurate answer would be to communicate with them directly.
Is there a way to do a DNS blacklist lookup instead?
I do not know, nor, does it seem anybody else, else a solution would have been provided in the previous threads.
There are many inquires in this forum for pr---es, simply because the SE's pick up the word and the results attract additional inquires. Traditionally speaking, there has been very little discussion of that same topic in this forum (and even less solutions), yet the inquires keep coming.