In order to avoid missing unread messages, it would be useful to have them marked in a different color. It would be great to be able to mark a read message as unread also, in case follow-up is still needed.

I love Hostfully, I would like that in the messages part of the cell phone app, unread messages could be seen in a different color to know that they have not been read and not leave messages unread

I'm surprised that this global inbox standard isn't already a feature, but to add to this- the message should remain bold until that specific user has read the message. For example:
a new message comes into the inbox of user A and user B. User A reads the message but user B does not. In this instance, the message should remain in bold for User B. This is vital as we now rely on the Airbnb app and the Pulse app which negates the need for a PMS