IT Pro Research today published a survey of 1781 email users in Japan. It’s not exactly clear who they were surveying (I am assuming enterprise/business users but…) so this is certainly not gospel.
Unsurprisingly, the total usage of Windows (from 98 through to Vista) is 96.8%. I know Macintosh has a larger than 2.1% share in Japan so this data is skewed towards business users I think.
The share of email clients is much more interesting and Thunderbird has an 11.5% share. Webmail has a 7% share.
If one was to do a general survey of Japanese Internet users, I’m sure the webmail percentage would be much higher and I’m sure there are many, like me, who use both a client and webmail.