Mail System Error - Returned Mail

[MAILER-DAEMON]

The original message was received at Tue, 23 Jan 2007 09:37:29 +0200
from linux.cz [219.130.35.238]

----- The following addresses had permanent fatal errors -----
<redhat-cz na linux.cz>

----- Transcript of session follows -----
  while talking to linux.cz.:
>>> MAIL From:"MAILER-DAEMON" <postmaster na linux.cz>
<<< 501 "MAILER-DAEMON" <postmaster na linux.cz>... Refused