Mark Read Messages as Unread There doesn’t appear to be any way to mark read messages as unread on the iPhone but there is, its is not clearly visable.
While viewing a message, tap on Details (this is located to the right of the `From` details, it may read `Hide`, if it does click on `Hide` & `Details will appear),
This then displays a blue dot with `mark as Unread option next to it (this is located just below the Subject Title)
Just tap on `Mark as unread`
The next time you view your inbox, the message will display a blue dot, which indicates that the message has not been read.