Opt-in e-mail advertising or permission marketing is a method of advertising by electronic mail wherein the recipient of the advertisement has consented to receive it. It is one of several ways developed by marketers to eliminate the disadvantages of e-mail marketing.
E-mail has become a very popular mode of communication across the world. It has also become extremely popular to advertise through. Some of the many advantages of advertising through e-mail are the direct contact with the consumer and it is "inexpensive, flexible, and simple to implement" (Fairhead, 2003). There are also disadvantages attached to e-mail advertising such as alienating the consumer because of overload to messages or the advertisement getting deleted without getting read.
A common example of permission marketing is a newsletter sent to a firm’s customers. Newsletters like this are a way to let customers know about upcoming events or promotions, or new products. In this type of advertising, a company that wants to send a newsletter to their customers may ask them at the point of purchase if they would like to receive this newsletter.
The above definition comes from Wikipedia and is subject to the GNU Free Documentation Licence.