The Java messaging service (JMS) is a middlewareoriented messaging technology working according to the publish/ subscribe principle. If subscribers install filter rules on the JMS server, JMS can be used as a message routing platform, but it is not clear whether its message throughput is sufficiently high to support large-scale systems. In this paper we investigate the capacity of the Websphere Message Queue JMS server. In contrast to other studies, we focus on the message throughput in the presence of filters and show that filtering reduces the performance significantly. We also present a model that describes the service time for a single message depending on the number of installed filters and validate it by measurements. This model helps to calculate the system throughput for specific application scenarios.