Connected gateway servers relay an electronic message from a first client device to a second client device by storing the message in respective user message queues associated with the sender and/or recipient of the message and then sending the message along a sequence of gateway servers to a gateway server that hosts the second client device. Upon receiving the electronic message at a first gateway server, a second gateway server that is hosting the second client device is identified and a sequence of gateway servers starting at the first gateway server and ending at the second gateway server is determined. Each gateway server in the sequence relays the message to the following gateway server in the sequence while maintaining user message queues. Failure of the last gateway server in the sequence results in the penultimate gateway server in the sequence assuming the responsibility of hosting the second client device.