who is your host? should be the name after the @ symbol in your email address (*@hostaddress.com)
I know that with GMail it's smtp.google.com and it requires encryption...
either encryption has been turned off, the outgoing server address is wrong, it's set to the wrong port, or something else. It's hard to tell, but I can try to locate the info.
I did a quick search and the first hit said that yahoo! mail is most popular in japan, so I found the instructions for it
hit "f10" on your keyboard to enable the toolbar, then click on "Accounts" in "tools..."
double-click on your account
in the "servers" tab (2nd), make sure that the "my server requires authentication" (bottom) is checked
Outgoing server: smtp.mail.yahoo.co.jp unless it it Yahoo! BB account: ybbsmtp.mail.yahoo.co.jp
click on "advanced" (last tab) and make sure this is correct:
outgoing mail (smtp): 587.
check "this server requires authentication"
the original tutorials may be easier to follow translated Original