The effect of PC e-mail usage on social tolerance was investigated by analyzing representative survey data collected from electorates in Yamanashi Prefecture, Japan. The results showed that PC e-mail usage had a positive effect on social tolerance because it allows for mediating communications with heterogeneous others. These results are a clear-cut contrast to previous research, which showed that mobile-phone e-mail usage had a negative effect on social tolerance because of the increasing homogeneity of personal networks. The results indicated that while the technological limitations of mobile phone e-mail usage selectively strengthen communications with homogeneous others through the exchange of short messages, PC e-mail usage facilitates communications between heterogeneous people, because it is suitable for the exchange of the longer messages necessary for sharing the assumptions made during correspondence. From the viewpoint of nourishing "bridging" social capital, it is suggested that the promotion of PC e-mail should be encouraged by establishing appropriate policies and that the functional development of the use of the Internet on mobile phones should be empirically investigated.