In this thesis, we learn in more detail about the functioning of the e-mail system, the role of the DNS, and the vulnerability of the SMTP. In order for the service to run smoothly, a suitable protection of the mail server is significant. Server certificates and SSL play a central role here. An additional way is achieved by e-mail authentication. To this purpose, we presented a variety of authentication mechanisms, SPF, DKIM, and DMARC. SPF checks the IP address of the sender and determines whether he or she is authorized to send e-mails with that identity. DKIM adds a digital signature to the sent e-mail and secures the content of the message. DMARC mechanism is based on the results of the two aforementioned authentication mechanisms. It specifies the rules for the destination server of the received message, dictating what action it should perform on it. We carried out the implementation of these mechanisms and tested their performance.
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