Registration Email

hello , Please help me !!
Im new to joomdle
Im having this problem that when a guest registers on the children registration page it registers him but does not send the email to the user
it says:
Notice
Could not instantiate mail function.


Message
The user was created

1. I have tried switching to sendmail from php mail but that doesnt help either
2. From moodle I opened : site admin->plugin->manage authentication and selected the option of SELF REGISTRATION as both email-based-self-registration and joomdle but the error still remains.

Could not instantiate mail function suggests you have a problem with your mail configuration in Joomla. There are a few options you can choose for mail which also relate to your server's configuration.

You can see many discussions and solutions on this
www.google.com.sg/search?q=Could+not+ins...10&es_sm=93&ie=UTF-8