1. An image processing system comprising: a server apparatus connected to a first network; an image processing apparatus connected to a second network; and a gateway apparatus configured to connect the second network to the first network, perform mutual conversion between a first communication protocol being used in the first network and a second communication protocol being used in the second network, and relay communication between the server apparatus and the image processing apparatus, wherein the server apparatus includes: a transmitting unit configured to transmit job data of a job by the first communication protocol, the image processing apparatus being made to execute the job; and an adding unit configured to add content information to the job data, the content information indicating contents of the job, and the gateway apparatus includes: an analyzing unit configured to analyze the job data and acquire the content information; a determining unit configured to determine whether the image processing apparatus is capable of executing the job based on the content information; and an executing unit configured to execute an operation related to the job based on a result of the determination performed by the determining unit.