>>358
http://help.yahoo.co.jp/help/jp/mail/anti-spam/anti-spam-49.html
http://help.yahoo.co.jp/help/jp/hosting/light/mail/mail-35.html
http://help.yahoo.co.jp/help/jp/hosting/light/mail/mail-16.html
etc.

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http://support.microsoft.com/kb/881600/JA/