Try copying /var/qmail/control/me to /var/qmail/control/defaultdomain but I don't think that will fix it... is myhost.mydom.or.jp supposed to be valid? Also, have you tried turning on all vpopmail logging options?
>> Please post the output of /var/qmail/bin/qmail-showctl, that'll help >> me find your problem. > > Thanks. I didn't know about that command. > Its a little long, but here it is: (clipped)