Most of those are Virtual Group casinos, and they are indeed Rogue. iNetBet is accredited, and you did NOT receive spam from them.
We accept that rogue casinos are going to misbehave, so it is not surprising that Virtual group are selling off their player email addresses. A better experiment would be to try this with casinos NOT considered rogue.
Another thing worth doing would be to see what GROUP the casinos are in, so that you have a better idea whether it is group policy, or down to leakage from individual casinos.
Rival would be an interesting exercise, as they are not considered likely to do anything deliberately "bad", such as violating privacy by selling on player's details.
An exercise covering accredited casinos would also be worth while, you should find NO spam comes from these, but it would be worth finding out whether this is always the case.
Empty Fruities Astern Capt'n
Back to port for unloading.
Full Sails - before we get raided ourselves.
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