Headers for sections would make it much more visually appealing and easier to see how the list of messages are organized. See the Pulse texting app for an example. I love how it has a header for each section and sorts my pinned conversations at the top, followed by the conversations from today, then this week, and finally older conversations. So much easier to find things! Also options to filter or sort by read vs. unread messages. Everyone likes to sort things differently. Give users the option to customize this. But either way, please add headers to organize the list in a more visual way.