초보입니다...고수여러분 도와주세요..
저희 사용자가 어느곳으로 메일을 보내면 아래와 같은 에러 발생..
 > >    ----- Transcript of session follows -----
> > ... while talking to oyathene.komatsu.co.jp.:
> > >>> MAIL From:<hsryu@rec??dyn.com> SIZE=211306
> > <<< 451 <hsryu@rec??dyn.com>... Sender domain must resolve
> > ... while talking to akbrigit.komatsu.co.jp.:
> > >>> MAIL From:<hsryu@rec??dyn.com> SIZE=211306
> > <<< 451 <hsryu@rec??dyn.com>... Sender domain must resolve
> > <toshikazu_nakanishi at komatsu.co.jp>... Deferred: 451 <hsryu@rec??dyn.com>... Sender domain must resolve
> > ... while talking to griffine.kusco.co.jp.:
> > >>> MAIL From:<hsryu@rec??dyn.com> SIZE=211306
> > <<< 451 <hsryu@rec??dyn.com>... Sender domain must resolve
> > <tak-suzuki at kusco.co.jp>... Deferred: 451 <hsryu@rec??dyn.com>... Sender domain must resolve
> > Warning: message still undelivered after 4 hours
> > Will keep trying until message is 5 days old
> >