Though website analytics can be very helpful, they are sometimes misleading. Concerning email response rates and bounce rates, please keep in mind there are two types of bounces: hard and soft.
When your email fails because of a full mailbox or an unavailable address, that’s a “soft bounce.”
When the address itself is a non-existent one, then that person is no longer available…a “hard bounce.”
A simple exercise is to collect the bounces and send again the next day or so. The bounces that still exist probably are the hard ones that can now be deleted from your email list.