The purposes of this research were (1) to develop an application for an electronic documentary system, and (2) to assess the effectiveness of the electronic correspondence system of the Weapons Department, Education Division in an Infantry School developed. According to the program for improving the quality of the organization in the field of information technology, to have a correspondence management system that responds to work-from-home operations. Under the epidemic situation of the communicable disease COVID-19. Using the Adapted Waterfall Model development lifecycle concept, i.e. systems planning, systems analysis, systems design, systems implementation and maintenance. The quantitative research process collected data from a population of 201 in an Education Division, the sample group was personnel of the Weapons Department is 36 by using purposive sampling method choosing 2 groups, divided into 12 commissioned officer  and 24 noncommissioned officer. Data were analyzed using descriptive statistics by measuring the central tendency and distribution values from the content quality assessment results in system design and using inferential statistics to verify the hypothesis by t-test from the results of evaluation of functional requirement, functional, usability and security. The results of the research can be summarized as follows: (1) the result of the development of an electronic documentary system application found that the system can be used Content is complete, up-to-date, and responsive. Attractive design it is very suitable for use in the management of documents of the Department of Weapons at a good level. (average 3.99, standard deviation 0.11) and (2) the results of the evaluation of the efficiency of an application for the electronic correspondence system developed. Found that it can be used to record the transfer of documents issued at the order, certificate. Draft interactive documents signing documents and circulating documents is most appropriate. Interact with personnel with notification systems through communication channels. Document data is stored in a secure, organized database and search quickly, at a very good level. (average 4.28, standard deviation 0.41) and the mean difference test results of the efficacy evaluation between a group of the commissioned officer and the noncommissioned officer found that they differed in functional requirement test, functional test and usability test statistically significant at the .05 level.