[mail function]
; For Win32 only.
SMTP = localhost
smtp_port = 25
; For Win32 only.
sendmail_from = localhost
// ^ and even something like me@gmail.com
but it says
Warning: mail() [function.mail]: SMTP server response: 550 5.7.1 Unable to relay for xxx@gmail.com in C:\wamp\www\job1\test1\test2\untitled.php on line 5
What is your smtp server? XP doesn't have a built-in SMTP unless you are using XP Pro with IIS and it's SMTP server. If you're using the IIS SMTP server you configure it from the IIS management console (control panel - administrative tools).