depends on the TOS - If in the TOS there is a clause for selling or renting data then absolutely not. Now that being said if you are buying bulk email databases you are probably dealing with companies that like to live on the edge or atleast firmly in the gray area so do you really want that headache?
If the TOS are explicitly saying that the customers emails won't be shared, then No. But if not, you can buy and sell email lists, as it is considered a transfer of ownership (I assume only one party will use the lists, the seller should not have the rights to use them).