[Exim] error: Unknown local part

The message could not be sent because one of the recipients was rejected by
the server. The rejected e-mail address was 'jmiranda@???'. Subject
'asdfas', Account: 'louie@???', Server: '202.47.125.43',
Protocol: SMTP, Server Response: '550 Unknown local part jmiranda in
<jmiranda@???>', Port: 25, Secure(SSL): No, Server Error: 550,
Error Number: 0x800CCC79


what could be the cause of this error?

-- -
Louie Miranda
http://www.axishift.com