Return Path launched a behavioral targeting service tied to email marketing, according to ClickZ. The firm's PostMasterDirect email list rental service will now include information about past behavior of those on the lists. This will allow Return Path to sell subsets of email lists that, for instance, have previously clicked on an offer. This has the potential of not only increasing performance for advertisers, but also reducing the clutter many people on the list would otherwise find in their email inboxes. One test cited by Return Path showed two campaigns geared around a music offer; one run on a music-related list, and another off of a general list that was narrowed via past clicks on music-related offers. The general list applying behavioral targeting showed more than double the clickthrough rate. For now Return Path is not charging extra for behavioral selects, as it attempts to determine the service's value for a future pricing mechanism.