Cannot send email to outsider

When i submit a form, an email will send automatically to some specified account. Everything is smooth when sending to Outlook account, but if i send email to the outsider account such as yahoo, gmail, hotmail, there will get error. The error is as below:

Warning: mail() [function.mail]: SMTP server response: 550 5.7.1 <mrlow@yahoo.com>... Relaying denied. IP name possibly forged [115.134.181.91] in C:\xampp\htdocs\laksd\send.php on line 478

Anyone can help me to fix this problem??

Thanks!!

 

can I see the script for email?

 

i think it's an authentication problem with your smtp server. usually you get an error like that and it also says you do not have permission

 

The portion script is something as below:

$tostaff = $row

 

taminder:

Got any solution to solve with the authentication problem at the server?? How to get permission to send email to outsider??

Thanks.