The paper provides a detailed analysis of the change in the procedure for informing the participants in the case after the State Judicial Administration of Ukraine approved Order No. 28 dated January 23, 2023 "The procedure for sending court summonses, notices to the participants in the legal process in electronic form." It was analyzed which factors contributed to the approval of the new procedure for sending court summonses. Among them are listed such as: the introduction of martial law on the territory of Ukraine, insufficient financing of judicial administrations, the presence of the process of digitalization of the judicial system. The expediency of using Viber as a mobile application for receiving subpoenas, instead of Telegram, WhatsAPP, Signal, was studied. Reported to the Kyiv International Institute of Sociology, which recognized Viber as the most popular messenger among Ukrainians. It is indicated that it is possible to send subpoenas only if the party to the case does not have an official email address and on the basis of a written statement. The concepts of official e-mail address and e-mail of a natural person are delimited. As is well known, failure to notify a participant in the case deprives him of the right to defense in court. Therefore, the paper clarified problematic issues regarding the determination of the moment of service of a court summons. The practice of Ukrainian courts and the ECtHR was studied. The "presumption of knowledge" of a person who agreed to receive messages from the court via messenger is indicated. The possibility of problems when using mobile applications is noted. Such problems are - lack of Internet connection, unstable operation of the mobile application, malfunction of the mobile device, inexperience of Viber users, etc. It has been investigated why the use of a screenshot to prove the propriety of a court notice is questionable. It is not excluded that the possibility of sending court messages through messengers can be used as a basis for abuse by the participants in the case, in the form of deliberate delay of court proceedings. The decision of the ECtHR is given, where the court noted that the applicant is obliged to demonstrate his willingness to participate in all stages of the proceedings and to refrain from using techniques that are associated with delays in the proceedings. The conclusion states that the ability to send subpoenas and subpoenas via Viber is useful and effective, but there are possible risks of abuse by the participants in the case.