I know it won't support 4k but it should at least do 1440 right? I can't get higher than 1080p...

![enter image description here](https://i.stack.imgur.com/Vvs2K.png)

**UPDATE**:
I pressed alt and clicked "scaled" to unlock the extra resolutions as suggested by Buscar웃. It gives me more options but onfortunately still nothing higher than 1080p :(

![enter image description here](https://i.stack.imgur.com/7qSHI.png)

This macbook is [quoted](http://support.apple.com/kb/SP658) as supporting "up to 2560 by 1600 pixels on up to two external displays" and it does so with the thunderbolt cinema display. Surely it should be able to do the same with my new 4k monitor? If it matters, the display I'm using is the AOC U2868PQU. I'm not using "mirroring" as suggested by LaX.