This study examines the concept of rapport and investigates the relationships between employee emotional expression as an antecedent, rapport as a mediating variable, and relationship quality as an outcome variable. Specifically, the study identifies the effects of service employees' (professors') emotional expression and its authenticity on rapport in educational services, as well as the effects of rapport on relationship outcomes including trust and customer satisfaction. By extending the scope of application of service employees' emotional expression and authenticity to repeated service encounters, this study evaluates encounter outcomes from a relationship marketing perspective. Empirical analysis conducted on university lecture services showed that the proposed model yielded generally satisfactory results. The key variables—emotional expression and its authenticity—both had significant effects on rapport, and rapport was found to strongly influence customer trust and satisfaction. It was confirmed that the positive emotional expression displayed by frontline service employees at service encounters and its authenticity serve as a foundation for relationship marketing through the partial or full mediating role performed by rapport. Furthermore, the authenticity of emotional expression was found to influence employee trust not only indirectly through rapport but also directly. Additionally, positive verbal expression and its authenticity were found to have an interactive effect on rapport.