邮件服务器故障

嘿，伙计们，我正在尝试设置一个邮件服务器，这样我就可以使用我的php网络服务器发送电子邮件了。我想我已经设置好了，但当我尝试发送邮件时，我会收到这个错误：

Warning: mail() [function.mail]: SMTP server response: 550 The address is not valid. in C:'wamp'www'scripts'register.php on line 57

这是我在php.ini 中的邮件服务器配置

[mail function]
; For Win32 only.
; http://php.net/smtp
SMTP = localhost
; http://php.net/smtp-port
smtp_port = 25
; For Win32 only.
; http://php.net/sendmail-from
sendmail_from = admin@custombb.no-ip.org

这是我发送邮件的代码行：

$send = mail($to, $subject, $message, $headers);

日志错误：

"TCPIP" 3584    "2012-03-15 14:56:20.609"   "TCPConnection - Posting AcceptEx on 0.0.0.0:25"
"DEBUG" 3584    "2012-03-15 14:56:20.609"   "Creating session 10"
"SMTPD" 3584    10  "2012-03-15 14:56:20.609"   "127.0.0.1" "SENT: 220 custombb.no-ip.org ESMTP"
"SMTPD" 3584    10  "2012-03-15 14:56:20.609"   "127.0.0.1" "RECEIVED: HELO duncan"
"SMTPD" 3584    10  "2012-03-15 14:56:20.609"   "127.0.0.1" "SENT: 250 Hello."
"SMTPD" 868 10  "2012-03-15 14:56:20.625"   "127.0.0.1" "RECEIVED: MAIL FROM:<you@yourdomain>"
"SMTPD" 868 10  "2012-03-15 14:56:20.625"   "127.0.0.1" "SENT: 550 The address is not valid."
"SMTPD" 3544    10  "2012-03-15 14:56:20.625"   "127.0.0.1" "RECEIVED: QUIT"
"SMTPD" 3544    10  "2012-03-15 14:56:20.625"   "127.0.0.1" "SENT: 221 goodbye"
"DEBUG" 4080    "2012-03-15 14:56:20.625"   "Closing TCP/IP socket"
"DEBUG" 4080    "2012-03-15 14:56:20.625"   "Ending session 10"

是什么原因造成的？什么是替代方案？谢谢