Under the pressure of e-commerce, the delivery service is a fast-growing industry. In the long history of the postal sector, 2019 was a defining moment. As the sector's traffic, revenue, business models, and infrastructure continued to shift beyond recognition, trends that had been developing gradually for decades gained traction. The global economy has been reshaped by the fight against the COVID-19 epidemic. Governments took extreme measures in reaction to the fast increase in reported instances. In 2020, the pandemic had an unprecedented impact on the global economy, global trade, and cross-border supply networks, with a level of contraction not seen since World War II. ii. At the same time, because postal services have remained to work during most global lockdowns, their importance to people has grown. In addition, in several countries, ecommerce sales have surged, thus boosting demand for postal services. This paper determined Delone and McLean's Information system success model to measure the effect of system quality, e-trust on the reuse intention of the website-based delivery service in Mongolia. Data were collected by surveying 150 customers who had experience, using SPSS 21.0 and AMOS 20.0 statistic package program. The statistical results supported all four proposed hypotheses. The study confirmed that electronic service quality of system quality were significant predictors of e-trust.