If you have not received a certain email you can follow these steps:
1. Make sure the sender has not been blacklisted world-wide for Spam issues. If this is the case the sender would have received a bounced-back message with instructions on what to do.
2. Make sure you have not exceeded your mail quota.
*If you are using cPanel, log in to cPanel, go to Email accounts and check your mail quota;
3. Make sure your MX records are correct.