Opt-in Email is a kind of bulk or mass email that is sent to many people in the same time. Its aim is to advertise various things from the certain company’s offer. But the most important idea standing beneath that kind of advertisement is the fact that it is permission – based. Opt-in email is sent only to clients that agreed to receiving such messages because they are interested in the company’s activity – her new products or attractive offers. They may gain many benefits from that cooperation because they know about promotions and sales. And on the other hand the firms earns money thank to that clients. So that relation brings benefits for both sides of business. Opt –in Email is a part of email campaign that should encourage as many people as possible to use the company’s service or bought her product. But buying email sender software and sending those messages is worth investing money on it. What is more it is really nice and easy form of advertising anything because it does not need much time to prepare it.