Why "next" and "back" buttons in Mobile Outlook are reversed?

[Windows Central Question]

When you open any letter to view it there are 4 buttons below (ltr): Reply, Delete, Left, Right. Obviously for 'right-handed' people Right button should open next letter and Left - previous. But for some reasons order is reversed. Do you know what is the reason? Is it UI/UX based decision?

 

[PepperdotNet]

The only sensible thing I can make of it is that you're looking at a list in reverse chronological order (newest at the top), so going forward would go to the next (older) message.