Well, first I have to congratulate you because you admit your mistakes. the measures they could take in this situation I think they already do a lot, it would not be feasible or easy for them to be controlling all addicted customers, I agree that addicted customers need to block emails from casinos and also need to be strong and resist , do not give in and play and then come to complain here on the forum.
In my experience people have the tendency to use the same email for everything and this is never a good idea, it is better to have a few so you can use them for different purposes and in the case it is necessary you could just abandon it and create a new one.
For example in the case of those that are addicted to gambling it can be difficult to abandon an email in which you receive work related emails but that you used as well to register at different casinos, as you will always be tempted to gamble, and even if you set up filters to delete those messages immediately those filters are not perfect so this could cause you to see one of those emails and then fire the desire to gamble once again, making your recovery way harder than what already is.