Sending emails does not work

Hello,

am using this plugin “Fast Secure Contact Form” (http://www.fastsecurecontactform.com/) to add a contact us form

But sending emails dosent work when i activate info@Domain-name -or any_email@domain_name– as a receiver although when i activate another email its work

on the troubleshooting information – it displays:
Test Message Sent
wordpress Test mail to …
Be sure to check your email to see if you received it.
See FAQ
The E-mail debugging output is shown below:
See FAQ
Could not instantiate mail function.

this plugin worked probably on other websites on the same server so i dont think its a server problem

Help!!