PHPmail extremely slow and sometimes fails

I currently have a very basic php page that loops through customer records (47 total) and emails them a small email using php mail. When I run a test email with just 2 customer it took one minute. It takes a total of 9 minutes to do 47 customers. After 11 minutes I still have not received an email. Is this normal? Is there a configuration change that could be made on the server? The list will be getting larger over time.