This happens when CNAME and MX records in the name server are not properly set. MX record is an address to the server when somebody sends an email to your domain. MX record should be the email server address that you use. You can add MX record by putting the email server or hosting server on Cloudbric Console > Settings > DNS. If you have your own email server, input its IP or domain. Then, make the CNAME settings all the same--putting email server address. Here are the images that can help you understand.
Basically, your mail settings (MX record) should remain as your original email server or hosting server, rather than Cloudbric's server.