Verify if an email (confirmation, cancellation, etc) was sent and / or received
There easy ways for a property manager to check to see if an email (confirmation, cancellation, etc) was sent by the BookingCenter system.
1) Use a CC and BCC solution such as explained at: https://support.bookingcenter.com/index.php?/Knowledgebase/Article/View/519.
2) Check for 'human error'. View the LOG to see if an operator actually sent a Letter. Look up the booking and note the date a Letter was actually sent. Often times, when a Guest states they never received it turns out that the Letter was never actually emailed
There may be times that you receive an email and a guest does not. There really is no way we can check if an email recipient opened or received an email. There are just too many vagaries in the internet to make any such assurances.