These days one clearly encounters e-mails more often than classic letters. The creation of the bibliographic reference itself is not difficult in any way, because e-mail servers or clients usually record the same technical information about e-mails (subject, information about the sender/addressee, etc.) However, it may be problematic to cite an e-mail without the possibility of identifying its sender (if the sender is not signed and the e-mail address does not provide a name and surname, etc.), because such texts lose credibility due to the fact that the sender’s identity cannot be determined.