You will need to be able to login to WHM on your server. This requires knowing the root password for your server. If you don't know the root password or haven't set one up, please see https://my.Bluehost.com/hosting/help/whm-login#root-password.
Login to the WHM by going to yourdomain.com/whm in a browser. Replace yourdomain.com with your domain.
Once you get to the login page, enter your username and password.
If this is your first time logging into the WHM, you may see a page titled "Feature Showcase". Click on Exit to WHM at the bottom of the page.The Feature Showcase page with "Exit to WHM" spotlighted.
Access Mail Logs
From the WHM home page, click the email icon.
The email icon.
On the email page there are several that give you information on email activity.
View Sent Summary:
The View Seny Summary icon.This tool shows the total number of message delivery attempts for each domain. This information is divided into successful and failed attempts, and shows the total number of bytes sent by each domain.
Mail Queue Manager:
The Mail Queue Manager icon.This tool allows you to view and manage email messages queued for delivery.
Mail Delivery Reports:
The Mail Delivery Reports icon.This tool allows you to find and review messages sent from and received by your server. You can see whether each message was delivered successfully. You can also view details about each delivery attempt.
With the information that you can access, you should be able to find out what happened to any message that went through your server.