I’d question the validity of any email list heck they are a valued commodity and any list worth while would not be for sale.
Not to mention that you would be advertising to individuals who did not sign up to receive “your” mailings and thus it would be considered spam.
Couple guys just got arrested for stealing/selling/purchasing email list, which the purchaser planned to use for online gambling spam.
So instead of purchasing just the list maybe youd want to purchase the entire newsletter/mailing scripts thus you could say it was actually what the subscribers signed up for.
Dunno! What I do know is I hate spam!