Newsletter Sending Error

[QIKAZZ]

Hey guys, I am getting this error on my website when trying to send a newsletter, I dont understand why as I have another database with a smaller customer list, and its working just fine. But I know quiet a few of my customers have received the email, but I feel some of the customers will not be receiveing the newsletter.

 

The is the error I get when I click the send mail.

 

Warning: mail() [function.mail]: Could not execute mail delivery program '/usr/sbin/sendmail -t -i ' in ***************/admin/includes/classes/email.php on line 523

 

Warning: mail() [function.mail]: Could not execute mail delivery program '/usr/sbin/sendmail -t -i ' in ***************/admin/includes/classes/email.php on line 523

 

Warning: mail() [function.mail]: Could not execute mail delivery program '/usr/sbin/sendmail -t -i ' in ***************/admin/includes/classes/email.php on line 523

 

I have tried searching but I cant find anything listed, ive looked through the email list and I cant find and invalid characters in the list, but the customer list subscribed to receive the newsletter is just under 500 customers.

 

Any help would be fantastic.

 

Cheers

 

Azz