Be cautious when renting opt-in e-mail lists.

Be cautious when renting opt-in e-mail lists for higher priced business-to-business products.

That's the advice of one leading newsletter consultant who rented 15,500 marketing titles for a "successful marketing newsletter."

Marlene Jensen of the Newsletter Group reported that only two people out of the 15,500 took up the offer for a "free issue subscription."

"My opinion of opt-in e-mail lists is that they're terrible for higher priced b-to-b products," she told NL/NL.

"I've decided that true vice presidents or directors of marketing do not agree to be on a double opt-in list that sends them two or more messages a day," she said. "And anyone with those titles who does so agree has probably lied about his or her title."