are you in the business of making investigations? then you have a budget

if it's a paid relay and the client asks for delete, then you gotta stop sending it out

but that doesn't mean that you can't charge for an extra service to access that data

as a relay operator, i have no obligation to send you anything unless i'm paid to do it and if you don't pay me extra why should i rat on my customers?

deleting spammy notes is necessary, because storage space is limited, and garbage is infinite

you just didn't think about how much volume it may entail, maybe?