Read status not syncing between devices

when i read an email on my computer, it shows as read on the computer but shows unread on my iphone. same in reverse - ie when i read an email on my iphone, it shows as read on the iphone, but shows as unread on the computer. i each case, it remains the same problem even after updating or refreshing on the device. They say it’s bc i use POP3 protocol to retrieve my mail. how do i change the protocols