If you did not receive the email send from a particular sender, the reasons can be either
1) The sender might be blacklisted from the spam organization.If this is the case there should be information on how to resolve the issue in the bounced-back email.
2) Your's email address might have exceeded the quota. Log into cpanel , go into your Email Accounts and check the mail quota of the email address.
3) The MX records might be incorrect.
