Trying to use Xbox One on my 1440p Monitor; Won't output at 1080p

So I just bought an Xbox One for black friday and I'm trying to use it with my Dell U2515H. It's a 24" monitor with a resolution of 2560x1440. When I connect the xbox to it and go into the settings, the display is set to 720p, and when I try to set it to 1080p, it just doesn't do anything, and stays at 720p. It looks terrible. Are 1440p monitors just not capable of outputting 1080p? Or am I not doing something right?

Submitted by bskilly Xbox 720 Release Date 2015