In dividing your list in this manner, you give yourself the ability to send more targeted communication. Some customers want both product and sales updates, while others might only want to hear about new versions. If you don’t give them the chance to choose, you risk losing them all-together. Since customers make the best buyers, it’s fairly obvious why you want to keep them subscribed to your customer email list.
A/B testing is trying two different techniques that communicate the same message on a small percentage of your list, seeing whether A or B performed the best, then using the better performing option when you email the rest of the list. It sounds complicated, but there are plenty of email marketing solutions out there that take all the math and guesswork out of it. (All you have to do is come up with the option A and option B you want to try.)
This is simplified, according to the IAB. Exchanges may try to unload unsold ("remnant") space at low prices through other exchanges. Some agencies maintain semi-permanent pre-cached bids with ad exchanges, and those may be examined before going out to additional demand side platforms for bids. The process for mobile advertising is different and may involve mobile carriers and handset software manufacturers.
Particular groups of customers can be targeted or even individuals. Offering individual customers special deals on merchandise and/or services on the customer's birthday, for instance, is one example of email marketing personalization. (A restaurant might send an email to customers on their birthday offering 50% off an entree,) Email marketing helps a business develop and maintain a relationship with a customer over time that hopefully results in increased sales and increased customer loyalty.