Gmails read on iPhone are not marked "read" on laptop

I have the iPhone 16 Pro Max, with latest software (18.6.2). Mail that I read on my iPhone are not marked "read" on my laptop when I use it. Very annoying. I saw elsewhere about making changes to Safari, but I do not have Safari on either my iPhone or laptop (so far as I can tell). This has been a long time problem, not recent. There are no exceptions. Read mail is never marked read.