At 14:15 06/07/1999 Monday -0600, you wrote:
|> Message from  yahoo.com.
|> Unable to deliver message to the following address(es).

Knowing when it FIRST started might be useful feedback.  You wrote
postmasters -- they didn't respond.

Maybe a telephone call?

http://www.networksolutions.com/cgi-bin/whois/whois?YAHOO-DOM

See also the YAHOO Contact Site:

http://docs.yahoo.com/info/support/contacts/

including "Eeks, a Bug!"

http://docs.yahoo.com/info/support/contacts/bugs.html