sendmail 에러 좀 봐주세요

mailx -v allfusion@fffff.com 이케 하면

>> MAIL From:<root@tim>
503 <root@tim> : invalid domain_part : FQDN required.
/dead.letter... Saved message in /dead.letter
Closing connection to mail.sktelecom.com.

이런 에러가 나오고

또 다른 에러는

tim /etc/mail>mailx -v allfusion@fffff.com Subject: test
test
.
EOT
tim /etc/mail>meteor4@chollian.net... Connecting to mailhub.chollian.net. via e.
220 mailhub1 ESMTP Terrace Internet Messaging Server 3.3200.0000 (for Chollian)
>>> EHLO tim.
250-mailhub1 Pleased to meet you
250-SIZE 47185920
250-8BITMIME
250-HELP
250-PIPELINING
250-AUTH
250-AUTH=LOGIN
250 ENHANCEDSTATUSCODES
>>> MAIL From:<root@tim> SIZE=63
553 5.1.8 Requested action not taken: mail box name <root@tim> not allowed.
/dead.letter... Saved message in /dead.letter
Closing connection to mailhub.chollian.net.
>>> QUIT
221 2.0.0 mailhub1 Service closing transmission channel

이렇게 나오는데 좀 알려주시면 고맙겠습니다..