A server which delivers emails can receive emails addressed to a plurality of transmission destinations including portions that can be arbitrarily determined by a user as a transmission destination of each user. A writing threshold is obtained according to the rate of change of the transparency of the object. In one example, an in-service software upgrade may be performed between a first virtual machine and a second virtual machine without a managing virtual machine. The heat sink socket attaches to the printed wiring board using a screw attachment means, which also assures electrical connectivity to the spatial light modulator through a interposer element between the device and spatial light modulator.