How do I see how many subscribers did not receive the email
Log into your mail-list account, and click on the Show Delivery Statistics button.
Each recent message to the list is shown, along with how many emails were delivered, pending delivery or failed.
For those messages that had delivery failures, the failed address(es) will be listed below the message
Click on the email address to see the detailed delivery logs
The delivery logs in red were rejected by the ISP