Confirm first if the open-rate feature for broadcast messages is enabled in your system.

1. Go to the Broadcast Message Configuration settings. 
2. Under "Message Tracking and Statistics," check if the "Use Open-Rate Detection" box is ticked.

To see the open rate of broadcast emails, follow these steps:

1. You can view the open rate by clicking "Stats" beside the email under functions.
2. Click 'View details' to see which recipients have opened your email.

Keep in mind that open rates will only be reported if there is an image or header in your email content and the recipient allows images to display in their email client