If you would like to be sure your e-mail will be arrived you must signed the option you will ask confirmation of the receiver. In this case in the most case you will get confirmation from the receiver.
second way
You will ask confirmation directly from recaiver of the CSAs and PSAs like " I would like to know if my letter is arrived. Please let me know you read. Thank you" . Hopefully you will get answer and you make sure if your e-mail message is arrived.
