Adaptive text...sort of...
Finally, the Gmail app has adaptive text...well, sort of. If adaptive text worked as it should, text in this app would render exactly as it does in the default email app. Sadly, this doesn’t work. Without increasing your adaptive text settings, the text in Gmail is much smaller than text in other apps. And if you increase the adaptive text size more to compensate, then text in other apps is HUGE. Yes, it’s an improvement, but it’s still not correct.
Larry.McJ about Gmail - Email by Google, v5.0.180107