A new small step for Google in its mobile ambitions: it has tied up with KDDI, Japan’s No. 2 mobile operator, to launch an e-mail service based on Gmail in September. KDDI Corp., which uses the “au” brand name for its mobile service, will offer Gmail under the “au one mail” name. Like Gmail, the service will both online and on mobile, reports IDG.

The new service will launch just over a year after Google and KDDI began working together. In July 2006 the carrier added a Google search box to its EZWeb mobile Internet service.