I believe the behavior changed either in 26 or 26.1 but at least the send button changes to blue when you start typing in the subject field or the body of a message. But in 26.2 on my iPad that Send button (arrow) remains greyed out (top right of the screenshot) regardless of where you type. The button functions, the email will be sent, but it appears as if it’s an un-selectable item. I’ve checked my wife’s iPad on 26.1 and as soon as she types in the subject the button turns blue, but in 26.2 on my iPad it remains grey no matter where you type.