Returned mail: User unknown

[Mail Delivery Subsystem <MAILER-DAEMON@xxxxxxx>]

The original message was received at Tue, 10 Nov 1998 22:25:41 -0500 (EST)
from root@localhost

*** ATTENTION ***

An e-mail you sent to an Internet destination could not be delivered.

The Internet address is listed in the section labeled:
 "----- The following addresses had permanent fatal errors -----".

The reason your e-mail could not be delivered is listed in the section
labeled:
 "----- Transcript of Session Follows -----".

The line beginning with "<<<" describes the specific reason your e-mail could
not be delivered.  The next line contains a second error message which is a
general translation for other e-mail servers.

Please direct further questions regarding this message to the e-mail
administrator or Postmaster at that destination.


   ----- The following addresses had permanent fatal errors -----
<bmw@domain.elided>

   ----- Transcript of session follows -----
... while talking to krusty-motorsports.com.:
>>> RCPT To:<bmw@domain.elided>
<<< 550 rejected: administrative prohibition (failed to find host name from IP
address)
550 <bmw@domain.elided>... User unknown

   ----- Original message follows -----