Magento向客户发送订单电子邮件,我们没有收到通知

Whenever any order is placed magento sends email to the customer saying "thank you for your order" but we are not getting any notification emails for the order.

In the backend, I have configured emails in

System -> Configuration -> General -> Store Email Addresses<br>
System -> Configuration -> Sales -> Sales Emails

I have also tried setting the "Send Order Comments Email Copy Method" to "Separate Email" instead of "Bcc"

Also, we are unable to receive mails through contact form.

Note: we are using Magento 1.8

Any suggestions how can i solve the problem?