One of the marketing activities via the Internet is electronic mail. Electronic mail or e-mail enables the transmission of text messages and documents via the internet to the sender's address in a standard form (sender@server/domain). The content of the e-mail is formed according to standard elements (header and body). Electronic mail, in addition to mutual communication within the business, serves as a marketing tool and enables the sending of commercial messages to end consumers. Regardless of whether it is standard advertising or e-mail marketing activities, it is necessary that the user is familiar with the business of the company and that he gives permission for the use of personal data for further marketing purposes. In order to protect users, the General Data Protection Regulation (GDPR) entered into force in 2018. Many companies use this method to achieve more sales, raise awareness of the product/service, achieve more visits, collect information and other, but the introduction of GDPR brings new features when processing personal data. There are different types of content that are accessible to consumers, such as newsletters, special offers, promotional material for the media, special offers, sponsored messages, automatic responses and others. E-mail communication carries low costs, direct potential users to the website, individual communication and more. However, apart from the advantages that this method offers, there are also disadvantages such as spam. Spam means mass sending of messages with the aim of promoting products and services. It is necessary to avoid it because it is illegal access to users, which results in poor response and the creation of negative publicity. To determine the right marketing campaign, which will result in a higher contribution, we use "A/B split testing".