급질문입니당!!(제발)

원인이 무엇이죠? 아무이상이 없었는데 갑자기 이런일이......

The original message was received at Thu, 4 Jul 2002 17:36:47 +0900
from root@localhost

   ----- The following addresses had permanent fatal errors -----
izzyone2001@korea.com

   ----- Transcript of session follows -----
550 5.1.2 izzyone2001@korea.com... Host unknown (Name server: korea.com.: non-recoverable error)

The original message was received at Thu, 4 Jul 2002 19:52:13 +0900
from root@localhost

   ----- The following addresses had permanent fatal errors -----
izzyone@dreamwiz.com
    (reason: 550 5.7.1 <tsha@fumate.com>... Access denied.)

   ----- Transcript of session follows -----
... while talking to mx-r.dreamwiz.com.:
>>> MAIL From:<tsha@fumate.com> SIZE=819
<<< 550 5.7.1 <tsha@fumate.com>... Access denied.
554 5.0.0 Service unavailable