Mail code works yesterday and not today

[JJ Harrison]

mail($recipient s_separated, $this->subject, $this->message, $headers);

Gives me this error:

Warning: mail() [function.mail]: SMTP server response: 554 : Recipient
address rejected: Relay access denied in d:\webpages\cla sses\mail.class .php
on line 53

When i echo the above variables the line before the function is called the
values are:

$recipients_sep arated = lizner2002@yaho o.com.au
$this->subject = 'Test'
$this->message = 'TEST'
$headers = 'From: newsletters@tec eco.com <TecEco Newsletters>\r\ n'

Can anyone see a problem that would be causing this? (I can send mail using
OE through the same mail server.)


--
JJ Harrison
lizner2002@yaho o.com.au